Bile Bomb

"Give the infected a taste of their own medicine with this CEDA-developed gastrointestinal projectile. Any zombie you soak with this puke grenade will be swarmed by common infected."

"Grabbin' puke!"

- Coach

The Bile bomb is a new weapon appearing in Left 4 Dead 2. The weapon was first mentioned in the new achievement list here. The Bile Bomb can be found in Left 4 Dead 2 as a throw-able glass canister containing the unmistakable viscous green boomer bile. When thrown it summons the zombie horde to attack whatever it hits. In many respects it can be considered a tier two pipe bomb, having far superior horde attracting effects, but lacking an explosive payload.

If you kill one of the Hazmat Infected, they may drop one of these containers full of bile due to the fact that they were CEDA workers that were studying The Infection. Despite this, they can be found outside of Dead Center. The bile bomb will use the same inventory slot as the pipe bomb and the molotov

The bomb spreads Boomer bile on whatever it hits and the horde summoned by the Survivors will attack whatever is covered in bile, including other Infected. The HUD symbol for the Bile bomb is a bio hazard symbol. If the Bile bomb is used on an empty space, it will summon a horde and all of the local infected to the place where the bomb landed the Director will even spawn a horde if there are not a lot of Infected, the infected will ignore the Survivors so long as the bile is still in effect, making them easy targets. The Common Infected hit by the bomb will begin attacking each other, as well. The bomb can also help in tank fights as it call the horde to attack the Tank.

The bomb can also be used to confuse Special Infected as it will make any two SI which have been hit to fight one another as well as the oncoming Infected. When a bile bomb hits an Infected, Survivors will be able to see the affected Infected's aura. Throwing the Bile bomb on a Survivor will not draw a horde to attack; however, the horde will be drawn to the location where the bomb impacted.

There are two achievements involving the bile bomb; Septic Tank is achieved by using the bile bomb on a Tank, and Robbed Zombie requires you to pick up ten bile bombs dropped by CEDA agents you have killed.

Tactics

 * Obviously, throwing a Bile Bomb makes common infected easy kills, allowing you to conserve ammunition by using your handgun or melee weapon of choice on the distracted infected. This could also make them useful in combination with the Heavy Machine Gun.
 * Boomer Bile Bombs also distract infected for a longer time than Pipe Bombs, making them potentially more useful for situations where the Survivors need to run from one point to another with Infected attacking, such as a rolling crescendo, a finale when the rescue vehicle arrives, or a gauntlet finale.
 * While it won't kill a Tank, a Bile Bomb thrown at a Tank will cause common infected to slow him down and damage him. If you use this tactic, try to shove away the attacking infected instead of killing them. The Bile Bomb gets riskier and riskier with rising difficulty, due to the higher health of both the Tank and the lingering Common Infected after the bile wears off.
 * Using a molotov or gas can along with a Bile Bomb can help make it easier to clear out a lot of infected.

* Bile Bombs will likely be much more useful in Hard Rain than in any other campaign, where rain can put out fires from molotovs, and the Worker Infected ignore pipe bombs, but still chase Bile Bombs.
 * Be careful when using a Bile Bomb on a Witch. If you startle her, by the time the infected begin to attack, the Witch will probably have incapacitated or killed the thrower and run away, leaving you and your allies with an incapacitated teammate and a horde coming in. The infected and the bile(unlike a molotov) won't slow her down, either. However, if you stay out of range, she will not notice who threw the bomb, and will instead run away crying as the infected chase her down. Plus, when she does incapacitate a survivor, she would just be taken care of like if you or an ally just got incapacitated: Just fire on the witch while she's ripping the survivor apart until she's dead.
 * If you have a specifically powerful target, like a Tank or Witch, it is better use the Bile Bomb only when a massive number of Infected is already nearby. Otherwise, the Tank/Witch will probably be dead by the time your horde shows up, and then all you have is more targets.

Trivia

 * The concept for the bile bomb was mentioned by a user on the official Steam forums on . Credit for the weapon however has not been assigned, as there has been no proof that one single fan came up with the idea, or if Valve coincidentally created it.  It also shares similarities with a now infamous team fortress weapon
 * It is odd how bile doesn't go onto any types of Infected when the Boomer vomits on them or explodes near them, yet when you throw a Bile Bomb at a group of Infected, it seems to spread all over them. This, coupled with the shade of color and its lack of effect on the Survivors, may mean that CEDA altered the bile after collecting it, as stated in its official description, making it react with the ground or Infected rather than an uninfected human.
 * The bile moves around in the jar as you walk around like the rag and liquid in the molotov.
 * The "blinding" effect of the Boomer bile also affects players as Special Infected.