Duke Nukem 3D

Type these during game play (Not in console)

DNKROZ - Invincibility
DNSTUFF - All weapons, keys and items
DNAMMO - Fule ammunition
DNWEAPONS - All weapons
DNITEMS - All items and keys
DNHYPER - Steroids
DNUNLOCK - The door in front of you is unlocked
DNVIEW - view Duke in 3rd person view
DNSCOTTYxy - Warp to episode X level Y
DNMONSTER - All monsters disappear
DNMAJOR - Jetpack fuel
DNINVENTORY - All items
DNCASHMAN - Throw with money
DNSHOWMAP - Show the whole map
DNCLIP - No Clip
DNENDING - Teleport to the end of the map
DNRATE - Shows the FPS

Note: These do not work in multiplayer!