Type in the following codes during play:

MPCASPER	Invisibility	
MPVADER		Invincibility	
MPPLAYALLDAY	Infinite Lives Mode	
MPBUNZ		Makes Claw Strong	
MPFRANKLIN	Lightning Sword	
MPPENGUIN	Ice Sword	
MPAPPLE		Full Health	
MPGANDALF	Full Magic	
MPFREAK		Catnip	
MPKFA		God Mode	
MPLOADED	Full Ammo	
MPSTOPWATCH	Timer on the bottom of the screen	
MPPOS		Shows global position	
MPFPS		Frames per second	
MPOBJECTS	Shows # of objects on screen	
MPNOINFO	show/hide info for above 4 cheats	
MPLITH		Monolith logos & Music	
MPMONOLITH	Same as above 
MPLOGO		Same as above
MPMOONGOODIES	Bouncing treasure	
MPSPOOKY	Invisible to enemies	
MPHAUNTED	Enemies into ghosts	
MPSHADOW	Claw is a shadow	
MPSUPERTHROW	Super Throw mode	
MPHOTSTUFF	Fire Sword	
MPWIMPY		Claw is weak	
MPJORDAN	Mega-jumping	
MPBOTLESS	Toggles the background 
MPMIDLESS	Toggles the middle plane 
MPTOPLESS	Toggles the foreground	
MPINCVID	Increases resolution	
MPDECVID	Decreases resolution	
MPDEFVID	Default resolution	
MPJAZZY		320X200 resolution	
MPDEVHEADS	Shows developers heads in place of treasure
MPBLASTER	Full dynamite	

Thanks to Revolution readers Jan Wester, Dogus, and German Jakob!