Doom 1 cheat codes
IDDQD -- Invulnerability
IDBEHOLDI -- Temporary invisibility.
IDBEHOLDR -- Temporary radiation suit.
IDBEHOLDS -- Temporary berserk.
IDBEHOLDA -- Temporary automap.
IDBEHOLDV -- Temporary invulnerability.
IDBEHOLDL -- Temporary light.
IDKFA -- Full health, ammo, weapons, armor and keys.
Doom II cheat codes
IDDQD -- God Mode
IDKFA -- All Ammo + Keys
IDFA -- All Ammo No Keys
IDCLEV## -- Level Select (Replace ## with number of level)
IDBEHOLD# -- Power Up (Example: IDBEHOLDS gives you Berserk)
IDCLIP -- No-Clip: (You can pass through walls)
FHHALL -- Destroys all enemies except Lost Souls
idclev32 -- Wolfenstein 3D Level
Quake cheat codes
give R # -- Gives rocket amount of entered # (0 to 255)
give S # -- Gives shell amount of entered # (0 to 255)
give # -- Gives weapon to entered # (1 to 8:1=Axe, 2=Shotgun, 3=Super Shotgun, 4=Nailgun, 5=Super Nailgun, 6=Grenade Launcher, 7=Rocket Launcher, 8=Thunderbolt)
god -- God Mode
fly -- Fly Mode
cl_forwardspeed # -- Forward movement speed
notarget -- Enemies Can't See You
give combat armor -- Combat armour
Quake II cheat codes
Give All -- All Weapons
Map badlands -- Badlands
Give ammo -- Full ammo for all available weapons
Give dualfire damage -- Gives Dualfire Damage
Give ionripper -- Gives Ion Ripper
Give trap -- Gives Trap
God -- God Mode
Noclip -- Walk Through Walls
Half Life cheat codes
/impulse 101 -- All weapons and ammo.
/-reload -- Disables auto-reload
/+reload -- Enables auto-reload
/impulse 109 -- Control on-screen monsters.
/impulse 203 -- Delete monsters/NPCs
/developer 1 -- Turns on Developer Mode
/developer 0 -- Turns off Developer Mode
/map (map name) -- map selection