***This section used to be about ammunition but it has been changed***

The grenade launcher (also known as the 'Friendly Fire Cannon') is often misused. Many players do the following when they use this weapon:

• Fire at a single common infected
  
• Fire at teammates
  
• Fire at Boomers, Spitters, Chargers and Witches

All those lead to a waste of grenade launcher ammo. Boomers and Spitters can be easily killed with other weapons, so there's no point wasting grenade launcher shells on them. As for Chargers and Witches, GL shells are not very effective on them. Honestly, I don't recommend picking up the grenade launcher because of long reload time, limited ammo (you can't refill GL ammo at ammo piles), having to reload after every shot, and splash damage that can affect teammates.

If you do want to use it, however, here are a few things you should know:

• Use it on Tanks! Tanks take 3x damage with a direct hit from the grenade launcher (deals about 1000-1200 damage per hit)
  
• Use it to save teammates from Hunters, Smokers and Jockeys. The blast will kill/stumble the Infected, but will NOT hurt the immobilized teammate. Just make sure that no other teammates are around the immobilized teammate before firing.
  
• Pair it with Pistols or a Magnum. Melee weapons are also good, but you are better of having a sidearm than a melee weapon to have an easier time killing Boomers and Spitters.

Pain pills gives you 50 temporary health points which will decay over time. Most players frequently waste pain pills on themselves despite having 80+ health. The worst thing that can happen is that players heal themselves with the First Aid Kit right after taking their Pain Pills. It is OK if you don't know, and if you do it once or twice. However, I am talking about people who do that over and over again.

"Are you that stupid?"
-Monsoon, Metal Gear Rising:Revengeance

Seriously? You just wasted 2 important health items! Of course, when you find spares along your journey, then yes you can take your pain pills and grab the spare one (Only if everyone on the team has a temporary healing item - which are Pain Pills or Adrenaline Shot). Here are some tips on how to efficiently and effectively use pills:
- Take pills when your health drops below 40 HP
- Give your pills to a hurt teammate (below 40 HP)
- Alert your teammates when you find Pain Pills if you already have one

The Bile Bomb lures the Common Infected towards it when you throw it. It is a very useful throwable item when you are in a Gauntlet Crescendo Event. They are not as common as Molotovs and Pipe Bombs, so use them wisely. Sadly, you will often find players wasting them and luring a random horde for nothing. For example, there are only 2-3 Common Infected in a wide-open area, and a teammate throws a bile bomb, luring a random horde. You are not only wasting your time fending them off, but also wasting your Primary Weapon Ammo.

Another example is the Dark Carnival Concert finale. A bile bomb will always spawn before you go inside the stadium. Pick it up. You WILL need it. Most of the time, you will find one teammate wasting the bile bomb on the first horde after starting the concert. The best time to use it is when the chopper arrives to pick your team up. Use the bile bomb to cover your team's escape.

One other thing: DO NOT THROW THE BILE BOMB WHEN YOU ARE COVERED IN BOOMER BILE. The horde will still come after you since they are more attracted to a bile-covered survivor than bile bombs. However when the bile bomb hits the Infected, they will chase the bile-covered Infected instead. It is still recommended not to throw the bile bomb then you are covered in boomer bile because it won't do you and your team any good. Here are some tips on using Bile Bombs effectively and when to use them:
- When you are running towards the rescue vehicle
- When you are rushing in a Gauntlet Crescendo Event
- When you are trying to revive an Incapacitated survivor (When the horde is too much to handle)

Adrenaline Shots give you 25 temporary HP and 15 seconds of speed boost. However, you will find your teammates using the adrenaline for nothing. Even at 90+ HP, they would simply use it. For what? In fact, you need to save it for critical situations and when you need to rush through the horde.

For example, take your adrenaline shot for the final dash to the rescue helicopter in The Parish Bridge Finale. Combined with a pipe bomb or a bile bomb, it would make it easier for your team to get to the chopper. Here are some tips for the effective use of Adrenaline Shots:
- When in Gauntlet Crescendo Events, take your Adrenaline Shot to rush through the horde (just beware of Special Infected)
- When you need to revive an Incapacitated Survivor quickly (For example, the Finales of campaigns when the rescue vehicle arrives)
- When you accidently startled the Witch from a distance
- Running from the Tank when your health drops below 40 HP

The First Aid Kit heals 80% of your damage taken. Upon use, it removes all temporary health points and gives you permanent health points. Unfortunately, this is the biggest frustration ever - The rarest item in the game is wasted and you don't have any left. That's right - it is the First Aid Kit. In most games, you will often find out that once you loaded the next chapter, all the First Aid Kits are gone. The next thing you know is 1 person has 99 HP. If you don't know, that person with 99 HP is the thief who stole your team's First Aid Kits. Sometimes, they will give an invalid excuse which says "I am saving this last health kit for myself because I'm more important :p". Well guess what? That attitude is absolutely wrong and needs to be changed!

If you choose not to change, then:
"I was wrong. You're not greedy. You're BATS*** INSANE!"
-Raiden, Metal Gear Rising:Revengeance

You will often see players (mainly the inexperienced players) healing themselves when you or other teammates needed it more. Even at 80+ HP, they will still heal themselves. Trust me. This incident frequently happens. Even if you tell them to stop, they will not listen. What should you do? Votekick! It may seem harsh, but if that health hogger won't listen to the team, kick that player out of your game. It is the only way to do it, to ensure that your game is not ruined any further.

This is a problem in Hard Rain, since you will be returning to the same safehouse in Chapter 3. When you return, 2 new First Aid Kits will spawn. The First Aid Kits that you didn't pick up previously in Chapter 2 will remain. Let's say you leave 3 medkits behind in Chapter 2. When you return in Chapter 3, you will find 5 medkits in the safe house. If you consume ALL in Chapter 2, there won't be enough for the team on the return trip, which means there will be only 2 medkits.
(This paragraph is requested by a few players)

Here are some DON'Ts for the First Aid Kit:
- Heal at 40+ HP (unless there are spares*)
- Use 2 or more First Aid Kits at a time
- Heal right after taking Pain Pills
- Healing your healthy self instead of the injured teammate
- Find a first aid kit and think "Oh look, a spare medkit. Better heal myself!"
- Take someone else's First Aid Kit when they are deploying Explosive/Incendiary ammunition
*Spares - When the entire team is healthy (green health, 40+ HP) and everyone has a first aid kit (sometimes defibrillators). By "spares", I don't mean the 4 First Aid Kits you see in the Finale area. It is when you find a First aid kit when progressing through the Campaign.

For tips on how to use the First Aid Kit, you can refer to this guide: http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=127693480&searchtext=Proper+Usage+of+First+Aid+Kit
This guide explains everything you need to know about how to properly use the First Aid Kit

Thank you for viewing this article. It is not a guide, it just explains about what are the most wasted items in Left 4 Dead 2. All these are derived from my experiences in Public Campaign games. If you have anything to add, leave it in the comments section, and I will add it to this list.

Feel free to check out my other guide:
http://gtm.steamproxy.vip/sharedfiles/filedetails/?id=332641075

"Okay. Let's dance!"
-Sam & Raiden, Metal Gear Rising:Revengeance