Now during play type (case sensitive):

FLATBROKE 		Turns off shading
FLYMETOTHEMOON		Racing on the moon
GOURAUD 		Turns on gouraud shading
HAVEALL 		All items
INFINITELIVES 		Infinite lives (duh!)
INFINITEWEAPONS 	Infinite weapons (that was a tough one!)
MASTEROFTHEUNIVERSE	Toggles textures
OLDMACDONALD		Protect farm from jumping cows
SOLIDASAROCK 		Invincibility
SUPERDAISY		One shot kills
WHATSTHEPOINT		Dot texture mode 
WIREWEWAITING 		Textures off

Thanks to Revolution readers Tim "Cloud 99", Wilmar Luna, Randy Russo, boris of S.M.S, João Pedro, Luis Miguel, Erik Sanchez, and Robbert Uges!