Left 4 Dead PC Game Cheats

Cheats:
Pressing the tilde ~ key to get the cheats menu:

Input Buddha - No perishing.
Input give X - Give any item (where X = item name).
Input god - Get God Mode.
Input impulse 10 - Get all weapons and ammo.
Input nb_blind 1 - Invisible to Infected.
Input noclip - Walk through walls.
Input sv_infinite_ammo 1 - Unlimited ammo.
Input warp_all_survivors_here - Teleports all survivors to where you are.
Input warp_all_survivors_to_checkpoint - Teleports all survivors to the closest checkpoint.
Input warp_all_survivors_to_finale - Teleports all survivors to the finale.
Input warp_to_start_area - Teleport to the next chapter.

Defense:
While reloading any weapon, your survivor can attack using the melee button.

Fire Exploit:
The infected can't put out fires once they are burning; use the igniting gas cans on hard targets like Tanks and Witches.

Speed Life:
The Tank can be outrun by any survivor with green health, but the Tank can overtake any survivor with 50% of less life.

Respawn Health:
As a zombie, ditch any survivors until you see a message stating you're too far away. Now you'll be able to end your current life and then respawn.