Bile Bomb

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 The Parish. 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 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. 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

 * An obvious tactic that can be used is one to throw one, and while all of the Infected are swarming the impact location, the Infected make very easy kills. They will stand there for a long time, longer than a pipe bomb so you should have plenty of time to be able to mop up the remaining Infected with a infinite ammo weapon like a pistol or a melee weapon. Bile can also be a effective means of taking out a Tank; simply throw at the Tank and a horde will soon attack, dealing a lot of damage and slowing him down. If you use this tactic, don't kill the Infected going for the Tank, but instead simply shove them away. It can also be a useful pipe bomb alternative if you gun down the Infected before the bile cloud disperses.
 * Coupling a molotov with the bile bomb is a useful way of clearing out Infected when you are in a hurry, such as when you need to get from Point A to Point B, like in the first Cresendo Event of the Parish. The bile will attract the Common Infected for about as long as a molotov will burn.

Trivia

 * The concept for the bile bomb was created by a user on the official Steam forums on
 * It is awkward how bile doesn't go onto any types of Infected when the Boomer barfs on them or explodes near them, yet when you throw a Bile Bomb at Infected, it seems to spread all over them. This could mean that only the bomb can cause them to be blinded and not the actually bile the Boomer vomits. Similarly when you throw it at other Survivors, it does not cover them with the bile.