Cheat Codes
	iddqd           God mode
	idkfa           Very Happy Ammo (full ammo, 200% armor, all weapons)
	idspispopd      No clipping (walk through walls)
	idbehold        Menu (followed by S, V, I, R, A, or L for choice)
	idclev          Warp (followed by episode number and level number)
	idmypos         Display coordinates in hex
	idchoppers      Chainsaw
	iddt            Toggles Automap (use when viewing Automap)
				[normal, full, full with objects]

Command Line
	-loadgame <# of the game>       Loads game saved in Save Games screen
	-deathmatch                     Starts Doom as a DeathMatch game
	-skill <# of skill level>       Sets the skill level you wish to play 
						(1-4)
	-episode <# of episode>         Sets the episode you wish to play 
						(1-3)
	-config <pathname>              Allows you to load a configuration 
						file stored in any directory
	-nomonsters                     Play Doom with no monsters
	-respawn                        Monsters respawn 8 seconds after you 
						kill them!


This information was taken from The "Official" Doom FAQ v5.5, by Hank Leukart.