Enter one of the following codes in the "Cheat codes" password box that is accessed through the Help menu.

Effect	Password
Toggle invincibility	barnsley or waddawimp
Level select	nozzle or sputnik
Toggle collision	detection popov or ghostrider
Multiple cheats	clam_chariot or iwantitall
All weapons	welk or suckphoton
Toggle unlimited ammunition	Phaal or leadeaters
Full shields	batfinc or raincoat
Full ammunition and shields	yeahbaby
Toggle number display	drugssuck or frameholio