During play, press Ctrl + Alt + ~ to bring up the console, then enter the following:

god	God Mode
give all	All weapons, full ammo/health/armor
give keys	All keys
give weapon_bfg	BFG
give weapon_chainsaw	Chainsaw
give weapon_machinegun	Machinegun
give weapon_rocketlauncher	Rocket Launcher
give weapon_shotgun	Shotgun
give weapon_plasmagun	Plasmagun
notarget	Invisibility
doomhell	Skip to last level
noclip	Walk through walls
give doom95	Play Doom 95
freeze	Freeze screen
benchmark	Game benchmark
status	Game status
gfxinfo	Graphics card info
aviDemo	Saves a demo to an AVI movie file

Level Select Codes:
Enter the following at the console.

Spawn Monsters and Items:
Entering the following at the console.

spawn monster_zombie_maint	"Yellow Jacket" Zombie
spawn monster_demon_archvile	Arch-Vile demon
spawn weapon_bfg	BFG 9000
spawn monster_demon_cacodemon	Cacodemon... Demon
spawn weapon_chaingun	Chaingun
spawn monster_zombie_commando_cgun	Chaingun Zombie
spawn monster_boss_cyberdemon	Cyberdemon
spawn monster_zombie_fat	Fat zombie
spawn monster_demon_hellknight	Hellknight demon
spawn monster_demon_imp	Imp
spawn weapon_machinegun	Machinegun
spawn monster_demon_maggot	Maggot demon
spawn monster_demon_mancubus	Mancubus demon
spawn monster_demon_pinky	Pinky Demon (Cyber dog)
spawn weapon_pistol	Pistol
spawn weapon_plasmagun	Plasma Rifle
spawn weapon_rocketlauncher	Rocket Launcher
spawn weapon_shotgun	Shotgun
spawn weapon_soulcube	Soul Cube
spawn monster_zombie_commando	Tentacle Zombie
spawn monster_demon_tick	Tick demon
spawn monster_demon_trite	Trite demon

Cabinet Combinations:

Cabinet Number	Access code	Contents
001	396	Bullets
003	483	Grenades, plasma cell, security armor, clips
009	752	Large med kits, security armor, grenades, clip
013	586	Grenades, shells, clip, security armor
017	347	Shells, clip, security armor, large med kit
023	531	Armor shards, shells, large med kit
038	409	Security armor, clip, grenades
039	102	Security armor, clips
047	123	Clips, grenades
048	123	Plasma cell, ammo belt, large med kit
049	123	Armor shards
054	246	Grenades, security armor
054	142	Security armor, rockets, grenades
063	972	Plasma gun, plasma cell, small med kit
064	651	Armor shards, clip, plasma cell
078	364	Large med kits, clips, grenades
079	364	Large med kits, clips, grenades
103	259	Plasma cells, shells, large med kit
104	579	Rockets, security armor, ammo belt
112	538	Armor shards, cell, shotgun
114	715	Backpack, security armor, clip
116	972	Large med kit, security armor, plasma gun, BFG cell
116	624	Shells, bullets, plasma cell
117	624	Security armor, BFG cell, grenades
213	371	Shells, clip, plasma cells
21D	298	Security armor, rockets, large med kit, grenades
317	841	Security armor, large med kits, clips, rockets, bullets
386	836	Clip, large med kits, ammo belt, bullets
387	836	Clip, rocket, grenades, large med kit, security armor
452	571	Rocket launcher, rockets, grenades
666	372	Imp, security armor
669	468	Grenades, plasma cells, security armor
Martian Buddy 1	0508	Chaingun, ammo belt, security armor
Martian Buddy 2	0508	BFG, security armor

Modifying Doom III .def files:
Every weapon and enemy in the game has attributes that are stored in .def files found in the doom/base/def folder. By changing the values associated with these attributes, you can change some of the basic characteristics of the game. So, for example, if you changed the "damage" value in the monster_zombie_fat2 def file from 15 to 100, the fat zombies would become much more powerful when you played the game. Converseley, if you changed the fat zombie damage value from 15 to 1, the fat zombies would hit for practically nothing.

**Note** Modifying game files is only recommended for advanced users. Extensive modification of def files can lead to stability and playability issues. Before altering any files, make a back-up copy of the /def folder so that you can replace the edited files with the originals if you need to. You cannot join any multiplayer games if you're running a game with edited def files, however you can still host multiplayer games. The changes to your def files will then affect everyone playing in your game.