Cheat mode:
Use one of the following codes during game play:

Result - Code:

Invincibility - iddqd
All weapons, keys, ammo, and 200% armor - idkfa
All weapons, ammo - idfa
Berserker strength - idbeholds
Temporary invincibility - idbeholdv
Temporary invisibility - idbeholdi
Full automap - idbeholda
Anti-radiation suit - idbeholdr
Light amplification visor - idbeholdl
Walk through walls - idclip
Chainsaw - idchoppers
Level select - idclev(episode number)(map number)
Toggle full map; full map and objects; normal map - iddt
Display coordinates and heading - idmypos
Change music to indicated level - idmus(level number)

View network opponent location:
Hold [Alt] and type "iddtiddtiddtiddt" at the map screen.