Doom II Cheat Codes and Console Commands List has made a complete list of all the Doom II console commands. By pressing the tilde ~ key while playing the  game, you can access the  console. Then you need to enter the following codes and press the ENTER to make them active.

Console Commands
Code Effect
idfa [Weapons] All Weapons/Ammo
idkfa [Keys] All Weapons/Ammo/Keys
IDBEHOLDS [Pack] Beserk Pack
idclev31 [Bonus] Bonus Level
IDMUSxx [xx being a number] Choose Game BGM
IDBEHOLDA [Map] Computer Area Map
IDDT [Map] Entire Map
iddqd [Mode] God Mode
IDBEHOLDI Invisibility
IDBEHOLDV Invulnerability
IDCLEV xx [Where xx is the level number, like 05] Level Warp
IDBEHOLDL [Goggles] Light Amp Goggles
idclip [Clipping] No Clipping Mode
IDBEHOLDR [Suit] Radiation Suit
idchoppers [Chainsaw] Replace fists with Chainsaw
idmypos [Code] Show Position in Code
idclev32 [3D Level] Wolfenstein 3D Level