While playing, type any of these codes in.

IDDQD - God mode
IDBEHOLDx - Gain temporary ability. x can be I=invisibility, R=radiation suit, S=berserk, A=auto map, V=invulnerability, L=light amps
IDFA - All weapons and ammo
IDKFA - All weapons, ammo and keys
IDCLIP - Walk through walls (toggle)
IDCLEV## - Warp to level ##
IDMUS## - Change background music to track ##
IDMYPOS - Display location
IDCHOPPERS - Get a chainsaw