Left 4 Dead/Trivia

Useful Notes! Anything that requires more than two sentences to explain is and belongs on the other L4D Wiki.

Items and Weapons

 * Healthpacks: They heal 80% of your injuries(cancelling all temporary health) and reset your incap count, rather than healing an exact amount of health. The more health you have, the less effective healthpacks are.
 * "International" version weapons: If you come across a weapon you haven't seen before in L4D2, it's because you're playing with someone that has the German version of the game or are playing a sever that enables them.
 * (L4D2) A Bile-Bomb will spawn a horde if there aren't enough Infected nearby for it to attract
 * (L4D2) Using Adrenaline allows you to run at maximum speed, even when water or infected hitting you would ordinarily slow you down. (i.e. Hard Rain)

Infected

 * Hunter pounce damage: Not determined by how high above the survivors you reach, but rather how far the spot you jump from is to where you land.
 * Boomer vomit has a sort of cooldown effect. If a boomer explodes on someone that has been vomited on, the effects won't stack and will wear off when the vomit was timed to normally.
 * Teamwork is just as important for the infected team as it is for the survivors. If you don't attack with your teammates, even mediocre survivors will make all your attacks worthless.
 * All playable infected make noise when they spawn or attack. If someone killed you quickly after they spawned, they picked up on your location with surround sound and shot through a wall.
 * In L4D Campaign Mode, Tanks run faster on fire than survivors can run and have a scripted death after ~sixty seconds rather than take damage from the fire.
 * Different weapons have different effectiveness on tanks.
 * You can free Survivors from Hunters, Smokers and Jockeys with a melee attack.
 * Chargers must be killed for their victim to be freed.
 * When a Smoker is pulling a Survivor towards them, you can free them by meleeing the Survivor or the Smoker, killing the Smoker or shooting the tongue itself.
 * When a Survivor is snared by a Hunter/Smoker/Jockey/Charger, bullets will pass straight through them.
 * (L4D) You can distract a Tank from his incapacitated target with a melee attack (provided the incapacitatee isn't shooting the Tank)
 * A Tank will always chase after a Survivor using a mounted machinegun.
 * You can destroy the rocks thrown by Tanks with gunfire.

Survivors

 * Friendly fire adjusts depending on the difficulty (Easy is 0%, Normal (and Versus/Scavenge) is 10%, Advanced is 50%, and Expert is full damage).

Other Useful Notes

 * A Boomer's vomit ALWAYS overrides a Bile Bomb's effects, but not that of a pipebomb.
 * Witches will chase after someone who disturbed her, but she will always go after someone else if they set her on fire.
 * If you're directly between a Witch and her target, she might just jump you
 * Chainsaws and Guns will attract idle common infected to you due to noise.

Actual Trivia

 * The German version of the game is censored for violence, and is more difficult as a result (you can't tell if a Hunter is on fire because the flames would be censored) so a number of weapons are ported from Counter-Strike. The Australian version of the game is also censored, but they don't get bonus weapons
 * Hey Its That Voice: Most of the NPC Survivors are played by guys who also did voices for Team Fortress 2. For the curious the boat man is the Sniper, the infected helicopter pilot is both the Spy and Pyro, and the pilot in Dead Air is the Demoman and Heavy.
 * Bill is Father Grigori.
 * Zoey is also Cortana and Princess Peach. For some, it might feel funny to use a baseball bat as her.
 * Coach is Cutty Wise.
 * Ellis is Jamie Wright.
 * You might recognize Hugh Dillon (Nick) from Flashpoint or his singing career.
 * The crazy church guy is the Scout.
 * The infected have been voiced by The Darkness, The Hulk and Appa.
 * Valve is infamously known for their Valve Time where they either set a date for a release for something and it gets delayed (sometimes several times) or they don't mention a release date at all until the product is good and ready to ship out. Left 4 Dead 2 is one of the few exceptions to the rule; the game was released one year after the original Left 4 Dead due to Valve wanting to prove that they can release on a fixed schedule. This action caused a Broken Base and it's best to leave it at that.