The "Medic" is the seventh class out of nine in TF2 whose primary objective is to support other players in-game. The Medic can be considered to be similar in role to that of a cleric in PvP matches, as it heals other players and provides boosters that aid either yourself or others, such as Ubercharge. One way that it differs from MvM (Man vs Machine) is that not only is the Medic able to heal players but is able to revive a dead player as well (with the exception of oneself).

The Medic can be considered to be one of the most important characters due to the fact that his role can shift the tides of a battle, resulting in, hopefully, a positive outcome. The Ubercharges have drastic effects on teammates, quickly making oneself a force to reckon with, and almost unstoppable.

The considered top tier weapons are :
Primaries : Blutsauger (Combat Medic) Crusader's Crossbow (Everything Else)
Medigun : Quick-Fix
Melee : Ubersaw

Obviously, every Medic requires a primary. Some are, worse than others, and others are a godsend. The two syringe guns that are considered Top-Tier, are the Blutsauger and the Crusader's Crossbow.

The Blutsauger gives +3 health per hit, and damages the opponent, but has a drawback which only allows you to heal 1 health per second. Why is it so good? Because the Blutsauger is a rapid fire weapon, and can reap in some well deserved health whether retreating or going offensively. It's the go-to weapon for a Battle Medic.

The Crusader's Crossbow is basically a Long-Ranged Medigun. You fire rather accurate bolts which can heal from 75 to 150 health, depending on range. You now gain a little Ubercharge when you heal a teammate from it. If you have steady aim, you can potentially save a teammate from death, across the whole map.

The stock primary is, like all other stock weapons, decent at least. No quirks, and decent DPS, there are obvious upgrades but if you're F2P, it's alright.

The Overdose is basically trash. It's weaker than the stock Syringe Gun, and only gives a 20% faster move speed for you. When active. The little, "When Active" part makes this Syringe Gun basically useless. It's a little more viable now, but it's better to just stick with the Stock if you don't have the Blutsauger or Crossbow.

Arguably the MOST IMPORTANT part of a good Medic, the Mediguns. The Medigun is an all-purpose healing device. You left click to heal your teammate, and right-click to activate a charge. An Ubercharge has a wide variety of effects, depending on the Medigun. It can make you and your patient invincible or give a 100% crit rate.
All Mediguns except for the Quick-Fix, overheal a partner to 150% Health, as well as healing 24 - 72 Health per second, except, as mentioned before, the Quick-Fix. 10 seconds is needed to heal a player faster, and a total of 20 seconds to heal at max rate. The healing rate depends on when your patient took damage, and how long it's been since they last took damage. All Uber's except the Vaccinator, lasts for 8 seconds, the Vaccinator's Uber lasts roughly 2 seconds per mini-charge. As of the latest update, Meet your Match of July 8th, 2016, all Mediguns mirror the movement speed and blast jumps of allies. (I.E Scout's movement speed, and/or Soldiers rocket jumps and Demoman's sticky jumps.)

The stock Medigun makes you and your target completely invunerable to damage, aside from killzones of maps, like a cliff or saw. This aids in a push against the defending team, as you will take no damage from Sentry Guns, or anything else. You can still be knocked back however, so beware of Pyros, Soldiers, and Demomen, as they can knock you and your patient into a killzone, which kills Ubered players. It takes anywhere from 40 seconds to 80 seconds to fully charge, unless in pre-round.

The Kritzkrieg (My Personal Favorite) grants 100% Critical rate when charging someone. This is better for defensive play, as it charges faster, and deals 3x damage to players. Why is it better for Defense? Crits do NOT apply to buildings, so buildings only take base damage from a weapon. The offense team won't have time to deploy buildings if your team is aggressive, so the Kritzkrieg is a perfect medigun for Defensive play. It takes 32 seconds to 64 seconds to get a full charge. It's charge rate is 25% faster than the stock. It is also an achievement item, so good luck F2Ps! Taunting also grants you and additional 11 health, and an, "Oktoberfest!" Use this to save yourself from burning, unless you have the Amputator.

The Quick-Fix, is arguably the best. It heals 40% faster, and has a 15% faster charge rate. It does not heal Patients to 150% Health, but instead, 125%. The Ubercharge gets charged in 32 seconds. It always charges at max rate, unless the patient is being healed from another source. It's Uber prevents knockback and slowdowns, as well as a 300% faster heal rate. It's the best in competitive play, due to the ridiculously fast charge rate, and heal rate, healing at 33.6 Health per second, and at a max of 100.8 Health. (May not be true anymore due to Meet your Match update of July 8th, 2016.)

Lastly, the Vaccinator. It's bad compared to the other mediguns, if inexperienced, but good in the right hands. It has 3 modes and 67% faster Ubercharge rate. What do the modes do? They give a 10% resistance to damage, depending on the mode, which are, Bullet, Blast, and Fire. You cycle through with the reload button, which is in default, R. The Ubercharge blocks 75% base damage, and 100% crit resistance to the selected type. So if a soldier hits a charged Medic with Blast Uber, they take, basically, 25% base damage. The biggest flaw with the Medigun, is that it does not block melee attacks, and you will, almost always, be hit with more than one type of damage. It also has a 33% slower UberCharge rate on Overhealed patients, and a -66% Overheal build rate on patients. It is considered by some, to be the, "Pub-Stomper" Medigun.

Another important part of the Medic's Arsenal is his melee.

The Ubersaw is arguably the best. It has a 20% slower firing speed, but successfully hitting an opponent gives 25% Uber. That saves 10 seconds of building Ubercharge. It's also the only way a Medic can tauntkill. Successfully hitting an opponent 4 times in a row can get your charge faster than even charging Uber during the Pre-Round.

The Bonesaw is the stock melee. It's as fast as any normal melee, and just as viable. Nothing special here, except that it feels like it crits all the time. Just not as much as a Ham Shank or Frying Pan.

The Vitasaw is next. When you die, you can retain up to 20% uber. If you can do the math correctly, that's 1/5th of your uber. (It actually displays as 19% when respawned but, whatever.) It's downside is that, you have 140 Health instead of 150 Health. This is really helpful when you're being steamrolled by the team as it allows you to, basically charge faster than the enemy.

The Amputator. It's ability? +3 health per second, essentially bringing the Medic to heal at 6 health per second. Only when active though. This basically gives the Medic his own Medic, at the expense of having to hold it out. You can use this when set on fire by pyro, or bleeding. It's great for a retreat, and the taunt gives a wide area-of-effect heal. It can help your whole team pushing a cart, so they can all live, and builds Uber depending on how much health you have healed. It also deals 20% less damage but, it's more for support than anything.

Lastly, the Solemn Vow. Great for competitive play, where Team-Play is VERY important. The ability is to let the Medic see the health of enemy players. It's only down-side is that it's 10% slower at swinging. That's it. Call-outs in competitive. Basically useless in public servers, which you most likely will be playing.

The most basic of basic strategies.

Sometimes, it's best to pocket the best players. Sometimes, you're stuck with a bad team as a Medic, it happens. Pocketing is, basically, where you only heal one person and disregard others. It's fun during pubs with a friend, but I recommend not doing so unless there's only one good person, and no other teammates can do anything. It's a rude move to do so. Try to do your best at avoiding this if you want to win. If you have a friend and want to mess around and just to have fun, you can do this. Also, beware of spies. Spies can be healed by any healing entity when he's disguised as the enemy. Dispensers, Payloads, and you the Medic can heal a disguised enemy spy, which can also overheal him. Watch for suspicious movement and actions and spy check your target before healing.

First and foremost, do NOT just pocket Heavies. Heavies do make good partners, they are slow so you can stay with them, have a lot of health, and a large hitbox to take damage, as well as a giant minigun of death, but they are not the only people to heal. Always heal teammates. If someone is calling for Medic, heal them. If they're too far away, quickly switch to the Crossbow, and shoot them with it. It can also be used to Spy-check, as it will damage the spy and not display as heals, as well as make a hitsound. If you're out of combat and a teammate is just sitting around, low health, you can wait a little then heal, as waiting at least 10 seconds will double your heal rate.

For pocketed heavies, if you have a sandwich equipped, and your Medic is dying, press second-fire, (default : Right Click) towards your pocket. It heals as much as a medium health kit unless it's a Dalokas Bar, which heals as much as a small health kit. This can seriously help your Medic, even if they aren't pocketing you. Beware, though enemies can also pick it up.

Certain Mediguns are good for certain times. Most of the time, the stock is best for offense, Kritzkrieg best for defense, and the Quick-Fix and Vaccinator is all-around. However, if you notice that you keep dying through high amounts of damage, or dying a lot due to a certain class, switch to appropriate Mediguns. Quick-fix can heal a lot of, "little" damage, so if there's a kritzkrieg Medic on the other team, consider switching to the stock Medigun so you don't get blown to bits, or the Vaccinator. If your team is taking a lot of damage as a whole, switch to Quick-Fix so you can move around. If there's no sentry, and you want to kill, switch to the Kritzkrieg. You don't always need to do that in pubs, but it's there.

MvM is an entirely different mode. The Kritzkrieg is the best for this mode.

The most important part of a KRITZKRIEG upgrade, is the healing upgrade. This allows you to revive players and keep players alive. Consider upgrading this first, but not the ONLY upgrade.

The second most important is Overheal mastery. This basically gives players more health. You most likely will be pocketing one person, as soldiers, engies, scouts, and whatever other class there is, will be out of your reach. So you heal them to max health, and they can keep that health while moving around. This allows you to move away from the Heavy, which is best to pocket in MvM as he will most likely be taking the most damage.

The third most important is the shield. This blocks all incoming projectiles and deals a small amount of damage very quickly. Use this to help protect your Heavy from critical projectiles during harder rounds, or your engineer's buildings. You can have your Heavy in front of buildings to help double your use of your shield.

Next is canteen specialist. This allows you to share your canteens and reduce the cost of them. Combine this with an Ubercharge, and this allows you to use an Uber Canteen (Makes you and your target invulnerable) and 100% Crits. This chews through giants. There's a small oversight in the system. You can max out canteen specialist, buy the canteens, then refund. You spend as much as 45 credits per canteen. You MUST max it out and buy it, THEN buy the canteens. If you buy them at the same time, you still spend as much as 75 per Ubercanteen. You keep canteens even when you refund upgrades, so you can put one upgrade back into the canteen specialist and still have all 3. This is best when you only have so much money. You don't KEEP the upgrades, you just buy them, refund, and put one point into it when the time comes.

The last two are basically useless unless you're in higher rounds. 25% faster Ubercharge rate or 2-second longer Ubercharge. I personally go with 2-second longer. One upgrade brings 8 second Uber to 10 second, with 3 upgrade slots, this allows you to go up to 14 seconds long. You can use an Uber canteen and an Ubersaw to basically charge your Ubercharge much faster than the increased charge rate.

Some basic rules.

Heal your Heavy. He takes the most damage. Uber him the most. If you don't have him, pocket the Soldier. Help your Heavy get through to Giants and have him chew through.

Before the round starts, crit charge a demoman with the sticky bomb launcher to have him drop 100% crit sticky bombs. This sticks until either he dies, they get destroyed, or he blows it up. He doesn't need random crits or to be charged right when he explodes them.

Shield at the right times. If there are many robots that are shooting a lot at you and your team, that's probably a good time. We're talking about things like Rapid Fire giants, or 50 heavies or a Giant Heavy.

Try to revive everyone. You basically just heal the holograms for those who don't know. Ubercharging increases the speed you revive someone. Unless they're at the front-line where the bots come from, go to them to heal them.

Overheal everyone when you have the chance. If someone walks by you, take a bit of time to, go ahead and overheal them. It's important to heal them, and get them at max health. You don't need to go out of your way to heal them. If there's a quick break during the wave, you can move around to heal others.

Stock
Base Damage : 10 per hit; crits: 30
Rounds : 40 / 150
Specialty : Nothing

Blutsauger
Base Damage : 10 per hit; crits: 30
Rounds : 40 / 150
Specialty : Heals 3 HP per hit

Overdose
Base Damage : 9 per hit; crits: 27
Rounds : 40 / 150
Specialty : When active, increases move speed up to 10% depending on Ubercharge. (0 = 0% faster move speed, 100% Uber = 10% faster move speed.)

Crusader's Crossbow
Base Damage 38 - 75; crits: 113 - 225
Rounds : 1 / 38
Specialty : Bolts Heal Targets (Range Dependent)

Stock
Heals : 24 HP/s, up to 72 HP/s
Uber Duration : 8 seconds
Charge Time : 40 - 80 seconds
Uber Effect : Invulnerability

Kritzkrieg
Heals : 24 HP/s, up to 72 HP/s
Uber Duration : 8 seconds
Charge Time : 32 - 64 seconds
Uber Effect : 100% Critical

Quick-Fix
Heals : 33 HP/s, up to 100 HP/s
Uber Duration : 8 seconds
Charge Time : 32 - 64 seconds
Uber Effect : 3x Heal Speed, no knockback or slowdowns
Special Effect : Full Charge Rate

Vaccinator
Heals : 24 HP/s up to 72 HP/s
Uber Duration : 2.5 seconds
Charge Time : 24 seconds - 72 seconds.
Uber Effect : 75% damage reduction and 100% Crit resistance to selected damage type
Special Effect : 10% damage reduction to selected damage type

Stock
Damage: 65; crit: 195
Specialty: None
Drawbacks: None

Ubersaw
Damage: 65; crit: 195
Specialty: Gains 25% Uber per successful hit
Drawbacks : 20% slower attack speed

Vita-Saw
Damage: 65; crit: 195
Specialty: Retains up to 20% Uber upon death
Drawbacks: 10 less HP

Amputator
Damage: 52; crit: 156
Specialty: When active, heal an additional 3 HP per second
Drawbacks: 20% less damage

Solemn Vow
Damage: 65; crit: 195
Specialty: See Enemy Health
Drawbacks: 10% slower attack speed

You don't need to read this, this is just random things.

I may have missed a few things. Some of my things may be confusing, so you can tell me if you need me to clarify it. These are only basic strategies, and I don't play Competitive much, so I can't tell you Advanced strategies, or when exactly to pop. These strategies work most of the time, but nothing is guaranteed in any game or situation.

Disclaimer :
The weapon stats ripped from the Official TF2 Wiki. I did not edit anything into the wiki, nor own the wiki. I have not done anything to the wiki in any way.
Link to the Wiki : https://wiki.teamfortress.com/
Link to the part of the wiki I used : https://wiki.teamfortress.com/wiki/Medic