At the main menu, select "Options," then "Keyboard/Mouse." Enable "Allow Developers Console." During gameplay, press "~" to access the console. Type in "Sv_Cheats 1" and press "Enter" to enable the cheats. Then, enter any one of the following:
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god --> Invincibility

sv_infinite_ammo 1 --> Unlimited Ammunition

noclip --> Toggles No Clipping Mode

give pistol --> Get Pistol

give ammo --> Full Ammunition

z_spawn weapon_SMG --> Gives you the SMG.

z_spawn mob --> spawns a zombie horde

z_spawn --> spawns a special infected (infected names:hunter,boomer,smoker,witch,tank)

give health --> gives 100 health

give hunting_rifle --> gives hunting rifle

give molotov --> gives molotov cocktail

give autoshotgun --> Gives auto shotgun

give health --> gives full health

z_spawn tank --> Spawns tank at location of crosshair

z_spawn boomer --> Spawns boomer at location of crosshair

z_spawn smoker --> Spawns smoker at location of crosshair

z_spawn hunter --> Spawns hunter at location of crosshair

give pain_pills --> Gives pain pills

thirdperson --> Sets the camera to be in third person mode.

thirdperson_mayamode --> Sets the camera to be fixed in place while in either third person or third person shoulder mode. Enter once to turn on and enter again to turn off.

thirdpersonshoulder --> Sets the camera behind the shoulder in third person.

give rifle --> Gives you an Mk 47 (machine gun)

z_health --> Change Zombie Health

z_speed --> Change Zombie Speed

director_panic_forever 0/1 --> Enables/Disables never ending panics.

z_common_limit --> Sets the maximum amount of regular zombies

director_force_panic --> Forces a panic event

z_spawn zombie --> Spawns 1 Zombie

give first_aid_kit --> gives you first aid kit

give pipe_bomb --> gives pipebomb

give molotov --> gives molotov

give gascan --> gives gascan

give oxygentank --> gives oxygen tank

give propanetank --> gives propanetank

fire --> Spawns a lighted molotov right on the floor under you.

boom --> Spawns a active pipebomb under you.

firstperson --> Play in first person (default); this cheat is only necessary if thirdperson mode is enabled

z_frustration_lifetime <#> --> Sets the number of seconds until the player loses control of the Tank from not attacking survivors

z_tank_health <#> --> Sets the maximum health of the Tank

z_witch_damage <#> --> Sets the amount of damage a Witch's attack does.

z_witch_allow_change_victim <1/0> --> True/False setting that allows the witch to change targets instead or focus on the one survivor that alerted her first

z_witch_burn_time --> Amount of time before a burning Witch dies from fire (does not affect damage caused by fire)

thirdpersonshoulder --> Sets the camera to over-the-shoulder third person mode

director_no_mobs <1/0> --> No mob rushes

director_stop --> Shuts off all wanderers, mobs, specials, and bosses

tongue_range <#> --> (Default 750) Sets the maximum range of the smoker's tongue attack

sb_friendlyfire <1/0> --> Sets whether or not bots (and only bots) are allowed to do firendly fire damage

director_no_human_zombies 0/1 --> Disables/enables controllable Boss Infected on any map

retry --> You can unlock achievements while using cheats (after entering sv_cheats 1, enter retry so that it will restart the game with the cheats on)