We shall begin my upcoming series of Spy guides with one of the most difficult lessons of all (funny that). This is something I'm incredibly passionate about and as someone who plays Spy a hell of a lot in this gamemode, I'm getting ready to roll out as much as I can. Now before you go running off onto a server, you need to remember that Spy in MvM isnt for everyone, and if things go terribly it's a better idea just to change to something simpler, for the benefit of both your team and yourself.

• To survive joining in the first place.
  
• How to last out the first 5 minutes without someone yelling at you.
  
• The most effective weapons for the job.
  
• The long lost art of Moneyspy.
  
• The tricks of the trade.

Now by this point we know that random teammates are unreliable at the best of times and a downright hindrance at the worst. In normal games its not all that bad, you just have to trust them not to blow your cover or ruin your cloak. MvM is completely different, because now not only do you have to trust them not to get you killed, but you have to trust them not to kick you for playing Spy in the first place. This problem is easy to solve, just follow these tips:

Tip 1: "I'm Rich, please dont hate me."
Kinda just what it says on the tin. Take off that Gibus and replace it with something flashy, because while its painful to say, if you look good, people will probably trust you to be good, even if you're actually godawful.

Tip 2: Safety in Numbers
Always bring a friend to the server, if you've got someone to back you up when you say you're good at Spy they're a hell of a lot more likely to believe you.

Tip 3: "If I fail miserably I'll switch."
Tell people you're willing to switch if things go bad, this will usually subdue them for the wave, but if you do terribly you'll end up having to keep your word.

Tip 4: Ask Why and Stick Up For Yourself.
This is one of the single most simple and efficient methods I've found. Just ask them whats wrong with the Spy, because once again, it isn't the fault of the class, it's the fault of the players, and while there are many flaws with the class itself, people usually can't think of these on the spot.

Tip 5: Just don't be a dumb ass.
Kinda self explanatory. I'll go into further depth on this later; it's about your weapons...

Now you've secured your spot on the team, you gotta keep it. This is quite the herculean feat, so lets move onto the first real part; Your weapons.

MvM is one of the gamemodes where you do need to explain the weapons you're trying to convince people to use or not, so here's my guide to every Spy weapon in MvM! Enjoy!

Revolvers

The best:
The L'etranger
Before the nerf of the dead ringer this thing had no place in MvM, and like the other member of the Saharan spy set, should never have been used. Now however, the DR cannot be refilled through any other method than waiting, thus this gun is brilliant as a utility if you intend to use what is almost certainly the best watch for this gamemode.


Dispelling the rumors:
The Diamondback
With how overpowered it is in the base game, the Diamondback seems like the obvious choice.
"But it's crits on kill!" you say, and to that I say yes, but you can get a knife upgrade which does the exact same thing AND you can use a higher damage revolver.
"But the crits can be farmed from targets even if the backstabs don't kill!" you say, and to that I say yes, in the base game, but in MvM you can't do that in the one situation where it's useful which would be when multi-stabbing a giant, since that doesn't seem to count. You might be able to farm them off of uber medics, I don't know I've never tried, but while you're doing that you're much more likely to just die and bait your team once every bot in a 5 mile radius detects those stabs and targets you as the highest priority kill.
"But as an early game weapon it's great, you don't need to buy an upgrade to get the crits and they're stored for later, surely it's good there?" you say, and to that I say no. Just no. As spy you are higher priority to be killed than even a medic if you're spotted. If you try to farm crits for this early on and you'll be either wasting your time or turned into mincemeat unless you've upgraded sapper power - and even then you're still a sitting duck if another group shows up.
In short this weapon features an interesting and seemingly powerful mechanic which is typically not useful in MvM as the spy is just too squishy to use it effectively.

The worst:
The Enforcer
After its nerf in gunmettle this weapon has almost become a downgrade, with it now having to be disguised in order to make use of the damage bonus. Before Gunmettle, I would have said it would be one of the best available, simply for its use against tanks at a push, but not any more.

Other weapons:
The Ambassador
Before the nerf this was arguably the single best Spy primary due to it's crits on demand allowing you to deal with Sniper bots without having to waste time approaching them. Afterwards however this upside was irrelevant, meaning the need for consistent aim and the fact that it doesn't stack up well with the fire-rate upgrades made this weapon a mediocre choice.

The Revolver
No upsides, no downsides, the revolver doesn't have any problems. Either way, it's a Pretty good choice.


Knives:
Knives are difficult to explain, as they're really dictated by playstyle, which will be covered later.

The best:
The Knife
Simplicity is beautiful. In this situation, stock really does beat all. Useful for both giant busting and money collecting, this one's almost definitely the best for the job.


Dispelling the rumor:
The Kunai
The kunai is often said to be better than the the knife just because it has instant health on backstab. IT'S NOT; As I said earlier, you're not really supposed to be getting backstabs anyway. It's less of a money collecting and giant busting weapon, and more designed to take out large groups of small bots. Not a very useful way of playing this one, but fun if done correctly.

The worst:
The Your Eternal Reward
The reason behind this one is really just obvious; It's useless in MvM. The disguise cloak cost cripples the DR, and going disguiseless is a death sentence as the bots will shoot the Spy as soon as he is spotted, being the highest priority target. Its normal factors of instant disguising and hiding bodies are completely nullified in MvM in an attempt to balance it against the robots. Its only redeeming feature is spoiled by the fact that bots instantly detect a Spy who's backstabbed someone, and your disguise will take roughly a second to come into effect. Basically pointless, the YER is probably the single worst weapon in MvM.

Other weapons:
The Spy-cicle
Pretty much the same as the knife, the bots will still detect you on backstab and the ice statues become purely cosmetic. The reason I put the knife over this is because it has one downside that completely squanders it as a giant busting weapon, its ability to melt. This will completely rule out all your chances of destroying any giant accompanied by a Pyro. I'd suggest it more as a money collecting weapon, but even then bots do instantly detect a flaming Spy, even if you're on fire for a split second, meaning they'll still know you're there and target you immediately. Not bad, but the knife is probably the one to go for, as this changes virtually nothing and mostly just makes your life harder.

The Big Earner
Its speed is useful as a getaway method, but I decided against it on the grounds that the 25 health you lose can be a lifesaver against many bots, and the speed upside can be received by simply using the dead ringer or upgrading speed in general. Certainly not a bad option, but not the best.

Sappers:
There's really no difference between them, but I thought I'd include them anyway.

Its all the same
The Sapper
It stops the robots from moving and slows giants. That's about it.



The Red-Tape Recorder
It also stops the robots from moving and slows giants. That's about it.



Watches
In MvM none of the watches are bad, one is just better.

They're all good:
The Invis Watch
Simple and effective, there's very little you can complain about with any stock weapon.

The Cloak And Dagger
Since its buff in Gunmettle the invis and the C&D have become virtually indistinguishable in MvM, with both now capable of taking ammo packs, taking away their only real difference, which was saving ammo kits for your teammates.

The Dead Ringer
This is hands down the best available watch for MvM. The fact it's a straight up, self explanatory getaway device really just means that its functionality is perfect for the situation. Its usual downside of enemies hearing your incredibly loud decloak sound is erased by the fact that they can still only detect you from roughly the same distance of other cloaks. Its only real downside, the fact that it isn't invisibility on demand, is nullified by how gullible all the bots are, and the fact that unless you're really rushing things it will still have time to recharge for your next escape. Probably the best for most situations.

Now that I've explained which weapons to use and why, I'm going to be covering how and where to use them. All I'll say is that there aren't many loadouts I've found to work in MvM, so I'll probably cover the rest in a moment.
First though, I'm going to be covering the big one, the true one, the only real one, The Moneyspy...

NOTE:

Following this, there is a section about upgrades *thunder claps*, please remember that the upgrades I suggest are a guideline based off of what I personally know works and are NOT definitely going to apply to everyone. You think you have a better way of doing it? Go ahead and use it, I'm not going to stop you.

The moneyspy is the single most effective way of playing spy in MvM, with its only rule being not to interfere with small bots. You begin by, as the name suggests, collecting money, but as you have more cash to play around with you begin to become a giant buster, an effective killer of medics, and at times, a total miracle worker, being the ace up your teams sleeve and often stopping the bomb in the final moments, when no one else can.

• Any Revolver, but if using DR L'etranger is recommended
  
• The Knife
  
• Any Sapper
  
• Any Watch

Before we begin on our quest to moneyspy we have to lay down a couple of ground rules.

1: Dont Over Extend
Now to explain this, you have to think about what the spy is. He's the stealth class designed to kill unsuspecting targets, and to counteract that he's squidgy. An unnatural amount of squidgy. The other classes have things to protect them from their squidgyness, the sniper has range, the scout has speed and the engi has his sentry. The spy however has no fallback when in plain sight, and can die in a few shots from virtually anything at point blank range which just so happens to be the place he's supposed to be working. Now lets think about the bots, which show up and move in groups, detect backstabs and will typically outnumber you 10 to 1. So what will happen if you try to stab a bot thinking that health on kill will help you? You'll be peppered full of bullets and die before you've even had the chance to kill three of them; Not a good plan.
The first rule of playing moneyspy is that you have to lie low, its the only way you'll be able to live long enough to do your job properly.

2: Know Your Priorities
Now this is a point that i can't stress enough; You're a money class, and for the first wave that's about it. You can't pull off any sort of massive chain kill on the smaller bots because you're currently easy to kill and every moment you spend doing something you shouldn't be just means that more money has the chance to disappear, and in turn, more of your teammates start wanting to kick you. Your priority roughly goes like this:

• Money.
  Money is always top priority when it comes to playing moneyspy; It's in the name for gods sake. It's your job, so you need to ♥♥♥♥♥♥♥♥ well do it. You should only ever put lower priorities above this if you're certain the remaining money is where someone will pick it up, or if there is no one but you who can prevent a back-cap.
  
• Spy: Professional Janitor.
  Now when i say cleanup duty I mean one of two things. I either mean killing Snipers and Engis to prevent them from setting up or dropping your medic, or i mean killing bots that your team have either failed to notice gradually creeping behind their lines, or failed to stop from reaching the bomb site. The most common bots to do this are giant scouts, who can and will easily drop the bomb in a matter of seconds. Depending on the number of giant scouts id recommend buying some teleport to spawn canteens, just in case one or two get past.
  
• Giant Busting.
  This is more relevant for later waves where your knife is upgraded, so you can do some of the most damage of any class in the game when it comes to giants, with your ability to mop up giant scouts in 2 stabs (if of course your armor penetration is maxed and your team hasn't damaged them), soldiers in a good 4, and heavies in a rough 6.
  
• Spy: Professional Demoman.
  Remember that Demo? The one on your team who's barely pulling his weight? Yeah well he just detonated his stickies on a group of scouts and isn't re-laying them because he put all his cash into his grenade launcher. Now there's no stickies for the medics and somebody's gotta clean that ♥♥♥♥ up. It ain't gonna be the defending classes, they'll just make the medics pop. It ain't gonna be the Demo because he's too busy with his grenade launcher. It's gonna have to be you.
  
• Working Overtime.
  This includes anything that isn't your job, searching for spies, killing smaller bots, shooting the tank with your potato gun of a revolver, this consists of everything that can be done much much better by somebody else. If you're doing this you should either have literally nothing else to do, or you need to get your lazy ass back to work before somebody gets pissed off and kicks you.

Now that we've covered your priorities, lets get on to how you should be preparing for each wave. Remember, these are recommendations not for killing the giants to begin with, but for surviving masses of damage, since you're going to be running out into the crossfire.

The first wave is almost always the hardest part, because while the spy is one of the single most effective classes in MvM, he requires masses of money to be used effectively. The reason the first wave is so problematic, is that you don't have the money to upgrade yourself to have even the slightest potential to succeed. So whats your first job? Money management.

Upgrades
There's 2 things you have to take into account when buying upgrades, what way you're playing and what bots you're playing against (which I'll go into later).
As the moneyspy, your goal is to stay alive and get as much cash as possible, as fast as possible. The first mistake I see a lot of spies make is to upgrade their sapper. So often do you see people upgrade it first thinking its crucial. It isn't. If anything its one of the last things you want to upgrade. No, the first things you want to upgrade are movement speed once and health regen 1-2 times, followed by a single upgrade of resistance to the most prominent damage type, and another upgrade to movement speed if you have any credits left over. Depending on the map, a little extra jump height may come in handy also.
Now I know what you're thinking, "Javert, since you have a weapon that can instakill on attack, why not just use health on kill to survive, as it'll heal you faster?" to which i will re-direct you to the ground rule 'don't over extend', which clearly states that they will turn around, and they will kill you.

Top Tips
Keep towards the walls when trying to get around the bots, and do not go for money until there are less than 6 bots in a single clump, doing otherwise can easily get you killed.

The reason I have dubbed these the teenage years is because they're the waves where you'll begin to turn from a frail, easy to kill, money only player, into a team saving and giant busting machine.

Upgrades
Like last time, you still have to remember that you're fragile. This means no killing small bots unless necessary, and no rushing into fights guns blazing. By this point you want to begin giant busting, so you need to start upgrading your knife. Depending on what map and difficulty you're playing, you usually have around $1000 to spend on the second wave, and $1100 for the third.
Using the first $1000 I'd recommend upgrading armor penetration once followed by an upgrade to your movement speed, and one to each of the resistances that show up in the current wave, upgrading some twice if it seems useful. I wouldn't recommend swing speed at this point as you're still too easy to kill, and you still need to be focusing on the money.
The third wave is when giants begin to run rampant, which is why I'd suggest now to be the time to spend the first $400 to upgrade armor penetration, the next $400 to upgrade swing speed twice, spending the last $300 on another upgrade of resistance. The sooner you stop being fairly easy to kill, the better.

Top Tips
When attacking any giant other than a scout during this transitional period, you should not go in for the third stab, and instead leave after attacking twice. Doing this will give you extra time to get away, and prevent an unnecessary death and the loss of money.

By this point you should have enough money to begin busting giants and collecting money at the same time.

Upgrades
At the 4th wave having two of the attack speed and armor penetration upgrades will usually be enough, and you should begin focusing on resistances, capping at the second upgrade for each resistance, although bullet is far less crucial than explosive, and fire is purely situational to the wave, and may not even be useful at all (you can upgrade the third either on crit res, or if theres and overabundance of a certain damage type, but otherwise it's not recommended) and the third for health regen (health regen should be purchased in relation to maximum health, E.G. you should only purchase +2 with the kunai whereas you should purchase +4 with the normal knife.)
For all waves up to the final wave DO NOT purchase anything for your gun or sapper unless you have spare money, with armor penetration and resistances being far more useful, and remember to keep money as your top priority AT ALL TIMES.

Top Tips
Remember that, while you are now capable of killing enemies safely, it is still your job to collect the money, and money conservation is still required. That $1 currency pack may not seem like much, but with the reduced bonus it can be the difference between your teammates getting a useful upgrade early on and just having to go without.

If you've made it all the way to the final wave, congrats on going against the meta!
And now, finally, you can stop being your teams ♥♥♥♥♥ and start killing things. Now, do you remember the list of priorities I mentioned earlier? Well forget about it, because the last wave has its own list of priorities:

• Giants
  Kill them.
  
• Medics
  Give in to your temptation.
  
• Giant Scouts
  Kill them all...

That's about it, so refund your ass and prepare to go kill some ♥♥♥♥.

Upgrades
The first thing you want to make sure you have is attack speed and armor penetration both up to their third upgrade, following which you should fully upgrade movement speed and purchase two upgrades to health regen. The remaining money should be used for required resistances, your armor penetration/attack speed, and jump height if necessary. Once those are complete, then you should begin to upgrade either your sapper, gun, or both.

Top Tips
First, remember to keep an eye on support classes; Surprisingly enough they seem to be the most often pitters if ignored, mainly because people assume they're not a threat and send down someone to deal with them who's using a gun which, while yes it does a lot of damage normally, does no damage at all thanks to the carriers combination of health regen and damage resist. If any bot gains all three of the bomb carrying bonuses killing it becomes your job.
Second, give up on the money. At this point all your team need it for is canteens, buybacks, and an achievement. Sure, you should pick it up if you spot it, or if its near you, but its no longer your priority.

Congratulations, if you've followed these instructions you're on track to be a fully functioning moneyspy! Now continue on with the guide, to learn of the other alternatives, and discover a few tricks of the trade.

I'm not going to be going into much depth on these playstyles, mainly because I'm not a fan of them, but I wont go without mentioning them. Now I'm not very supportive of alternative playstyles, because they tend to take away from what the class is generically designed for, but I'll support them if they have potential for success. So here's one of the only two alternative setups I support even slightly: The Vampire.

The Vampire is an alternative playstyle ripped straight from the normal game and planted in MvM, starting out as a squidgy mush and gradually becoming stronger and stronger with every stab. More designed to take out singular bot hordes than for giant busting, but has similar potential for money collection. More for fun than practicality, the vampire isn't the best way to play, but it can be semi useful at times.

• The Diamondback
  
• The Kunai
  
• Any Sapper
  
• The Dead Ringer

As before, I will now lay down some rules for what you should and shouldn't be doing

1: For The Love Of God, Don't Attack The Giants
Until later on you are hands down completely useless against them. With only 70 health you can be killed in a single shot, for a measly 376 damage on the giant. Just stick to the bots for the beginning and shoot the giant from a distance (that's right, I'm endorsing your gun in this one) if you really feel like you need to be damaging it. And to all of you thinking 'the diamondback picks up crits even on backstabs that don't kill, thus attacking giants must be great' I must repeat this: Not in MvM it doesn't.

2: Know Your Priorities
Similarly to last time, you have a set of priorities, which unsurprisingly is rather different, not to mention vastly less demanding than your last. It goes roughly in this order:

• Cleanup Duty
  Thought i was going to say money didn't you? well, as previously stated, this playstyle is more for fun than anything, and I thought I may as well put this up top because realistically its what you really need to be looking out for as the vampire. You're more for support than money and thus you should be ensuring that your team does not fail, be it due to an engis teleporter or a scout capping.
  
• Medics
  Since you should now be optimized to deal with smaller bots medics should be your top priority, as they're something you can quite easily pick off, saving your team time and effort.
  
• Money
  We all knew it was going to be pretty high up here either way. You cannot change a class with a specified job to make it not perform that job at all, and money still needs to be one of your focuses simply because you can do it far easier than most other classes.
  
• Overtime
  Yay, you can now play semi offensively, enjoy yourself and remember that the tank is the lowest priority bot you should be attacking.
  
• Giant Busting
  To put it plainly, if you try to kill the giants without having killed at least one bot before hand you will die. Not 'might' die, not 'could' die, you will die. Your health is too low, maybe come back after killing one or two things.

And Now, without further ado, we shall learn how to function as the vampire:

Get it? It's a joke about vampires drinking from robots? No? Well anyway, the first wave isn't quite as difficult as before, simply because there's a clear cut set of upgrades you want to begin with, and these are: One health regen, one movement speed, one projectile penetration, resistances if there's spare cash, and, as surprising as it is following my previous denial of its use, one sapper power. The reasoning behind these is simple. First, you only need one regen because you're using the kunai, both making you the source of your own health and cutting your health down to an amount that can easily be managed with only one of these upgrades. Second, movement speed is necessary because it's movement speed, of course you need it. Third, the projectile penetration is required to save on the crits used to take out bot hordes, as you will have only gained a few from your previous victims. Finally, the sapper power is required just to make sure you have a safe health source in case you get dangerously low.

Now, from second wave onwards you want to be focusing on attack speed, sapper power, your speed and resistances in general, and your gun. Armour penetration is something I wouldn't suggest in the early waves, mainly because its not really your job, but as the waves get further in I'd recommend getting at least two of the upgrade just for good measure, as you may very well need to mop up a giant scout that gets past.

For the final wave I may suggest changing loadout, mainly because of the usual lack of small bots in most maps. If you do decide to stay with this setup i have one recommendation of how to deal with the giants if they're accompanied by medics. You should begin by waiting for the giant to drop down, following which you should get as close to it as possible, at which point the medics should drop down. When the medics drop, sap the giant and begin slaughtering the medics, before running away with a good 3 to 6 crits and 200 health. Following this you should wait for the giant to become focused on your team again, before attacking it and getting in as many stabs as possible, retreating and waiting for the next set of giants, in order to repeat the system again.

Man, that portmanteau is a stretch, but whatever. Now, onto our final playstyle: The Spout

The Spout is an alternative playstyle in which you, of course, go 2fast. Similarly to the Vampire, this playstyle is more for fun than anything, but in some cases actually serves some practicality. With your lack of health once again limiting your ability to bust giants, its less useful than the moneyspy in some aspects, but may very well be better for collecting the cash due to its speed boost. This is of course, if you don't die straight after getting the boost.

• The L'etranger
  
• The Big Earner
  
• Any Sapper
  
• The Dead Ringer

The final set of rules I'll give out in this guide:

1: Don't Attack Large Groups Of Bots
Self explanatory really; You're a spy with 25 health below average and you're going to be racing around the enemy lines, and you can guarantee that the bots are going to be shooting at you if you start killing them. So what should you do about it? Make sure there aren't too many bots shooting you at one time. I believe I've said this before, but I would recommend you not move in, let alone attack, unless there are fewer than 6 bots in one lump at one time.

2: Know Your Priorities
Similarly to last time, you have a set of priorities, which unsurprisingly is rather different, not to mention vastly less demanding than your last. It goes roughly in this order:

• Cleanup Duty
  Once again, this is your job. Not because nobody else can do it (unless its a bot with all the full resistance/health/crit bonus that has the bomb, in which case you probably are the only one capable of stopping it), but because you can do it the best, the easiest, and spend the less time doing it without taking up the space of a more useful player elsewhere.
  
• Giant Busting
  This is more for later waves, when you have the ability to survive them. Giants are never recommended for the first wave, as you don't have the tools to kill them at that point.
  
• Money
  Really, money doesn't go anywhere on this list, because really, you're going to be collecting it idly with your continuous movement around the enemy lines.
  
• Medics
  Since you're optimized to kill smaller bots, and these tend to be the highest priority small bots available, you can kinda just put two and two together.
  
• Overtime
  You're optimized to kill smaller bots. Overtime is killing smaller bots. Need i say more?
  
  
  Spout: How Its Done
  And now, onto the upgrades.
  
  
  Wave 1: Gotta Go Fast
  This being a loadout based around speed and maneuverability, the first things you are going to want to upgrade are your speed and maneuverability. You should usually upgrade both speed and jump height twice, followed by a single upgrade to both health regen and health on kill. Whatever credits you have left over you should use on resistances. If you cannot afford a major resistance save the credits for the next wave or put them into another health regen/health on kill. You must remember that its safer for you to keep track of the cash on the first wave, as you can still die far too easily to go out and start killing things regularly. Its safer to kill the stragglers than to get yourself killed trying to stop the big groups early on.
  
  
  Wave 2 Onward: 2Fast2Quick
  Having gained about another 1000 credits on the second wave, you should now proceed to max your speed and jump height, following which you should upgrade resistances, health on kill once, and if you have enough credits left over, sapper power. The reason I place sapper power as the last option, is because its only real use is as either a crit farm if you're using the diamondback, or as a source of easy health if you're using the kunai. With the big earner however, you need to first have these upgrades and even then all it takes is one bot to activate your speed boost and you're home free, with the more time you spend trying to kill unnecessary amounts of bots making it easier for you to be killed by the few who haven't been sapped. Continue with upgrades similar to these for the following waves, remembering that resistances take priority.
  
  
  The Final Wave: Sanic
  And now its reached the best part of every mission, the final wave. Refund your upgrades and replace them with the following. Assuming you have roughly 5000 credits, you should upgrade the following: Max both movement speed and jump height, and upgrade all featured resistances according to the number of bots of each type, as determined by the map. If crits appear as anything more than a scout their resistance should always be maxed. Following this you should upgrade health regen twice, and health on kill three times, followed by two upgrades to both attack speed and armor penetration. Your remaining credits should be spent on upgrading your knife further, and on teleport to spawn canteens if there are giant scouts.

Now that we're done talking about singular playstyles, here's some tricks that can help out for any of them, whether it comes to collecting money, or getting out of a sticky situation in general. The premise to each of these tricks may be simple, but they can be really helpful at times:

This typically works best for getting away from critical heavies, as they can keep up a singular stream of bullets at all times, but it can work with pretty much any critical attack from any non-support class besides the pyro. Critical attacks give off an extreme amount of knockback, even from bullet attacks, meaning that if you jump as a critical attack is fired at you, as long as you survive, you will be launched away from the enemy at a rapid speed, helping you to survive incredibly dangerous situations at the press of a button. For bots like crit heavies also, it's useful to note that bots do not immediately lose you if you cloak, meaning that you can use this trick while cloaking to also reduce the incoming damage. This method occasionally works with non-crit attacks, but its vastly less effective.

Now when you're playing moneyspy, 5 credits may not seem like a lot, but losing even one cash wad loses you the bonus. So while you're going 'Even if i miss that 5 I'm still doing fine' you're not. Thats 55 you're missing in one package, not just 5.
Now lets say there's a credit pack pretty close to you that's about to burn out. You aren't going to be able to reach it in time normally, so you need to get there fast. A situation like this is why you should have the DR equipped, and assuming that you are, all you have to do is remove your disguise and pray that whatever hits you doesn't kill you. If all goes according to plan, your DR will activate, you'll be able to race towards the cash at breakneck speed and hopefully catch it before it burns up.

This one is more of a team helping one, but its simple none the less. Is your Heavy or Engi not on par? Are they not body blocking the giant scouts like they're supposed to? Sure, you could go sap it, but you may very well not catch it in time, or your sapper may have been used elsewhere. Why don't you go and earn some bonus street cred with your team and body block the scouts on your own. Why you, you ask? Well think about the normal body blockers: The Heavy and the sentry. What do they have in common? They both have masses of health and deal out masses of damage. So what do you have above them? You have the greatest gift of all, the scouts don't even know they're running into you. Scout gets in 8 swings on the heavy and he dies, which usually takes a good 6 seconds, by which point the bots been destroyed. How long will it take the scout to realize you're a spy, and in turn start to swing at you? A good deal more than 6 seconds, which means you may as well have as much health as him in this sort of situation, and the only thing you're not pulling off is his damage, which really doesn't matter, since you're doing this as the backup anyway, and your team should be grateful for that to begin with.

Well, if you've gotten this far, Congratulations! Now you're ready to go out and smash MvM as the Spy. To Reiterate what i said at the beginning, Spy isn't for everybody, and in some cases both you and your team may be better off if you played something simpler. But hey, nothing can stop you from learning. Did I forget about something? Have any big questions? Ask me below and I might answer your question.

If you liked this guide, or learned anything you didn't know be sure to spread it around, and raise awareness that MvM Spy can be better. Also be sure to follow me, because I may well make another guide in future, you never know!

And now, responses to general questions:

• Someone brought to my attention the fact that I did not mention canteens in this guide. This is for one simple reason, 3/4 are effectively useless as spy.
  Krits has no place in his arsenal, both as a class that cannot deal reliable ranged damage, and for the fact that for the price of 3 canteens he can purchase an upgrade which will do the same upon use of his knife, also allowing him to chain kills.
  Refill clips and ammo should never have a reason to be used, as if you are using your gun this much you are likely in a last ditch situation anyway and will probably die immediately afterwards.
  Ubercharge can be useful in cases where getting in and collecting the money are going to result in your death, however with proper timing these situations shouldn't typically occur, and for the cost it is very ineffective.
  Finally, teleport to spawn is actually very useful to Spy, as it allows him to quickly return to the hatch and prevent a back cap, which can often be a godsend if one bot just so happened to get through. I would definitely recommend having at least one of these on you whenever you have the spare money.
  
• I see a lot of Spies buying into sapper power thinking it will be of great use to them, so I feel I need to make this absolutely crystal clear:
  Sapper Power is not mandatory and should not be relied on or even purchased without a good reason.
  The Sapper is a weapon that can be incredibly useful in a series of niche situations, however outside of these it is fairly useless, and ends up taking up a substantial amount of your money that could be much better spent elsewhere.
  The situations where it will be of use are:
  
  • If your team are incompetent, for example if your Demo is incapable of destroying Uber Medics. If nobody else can manage, it's your job, and Sapper power can make this much easier.
    
  • If there are any fake giants that spawn together in groups, by which I mean bots with large health pools that are treated as regular bots, and can thus be killed in a single stab (for example Fists of Steel Heavies). In this case, sapping these bots will disable them just like any other, meaning you can actually kill them far faster than any of your teammates
    
  • The final wave, where money is a-plenty. It's a much better choice than upgrading your revolver, so go right ahead.
  For clarity, it does not increase the recharge rate of the Sapper, meaning it is not of much use for slowing giant Scouts which typically come down individually.
  The Sapper is a niche, support-type weapon, and it should be recognized as such and used accordingly.