Various Cheats:
When the cursor is over the Hints for Videogames book on the inventory, press these codes

PATRICKMARLEY - Hear Darnley Microcorder

QUICKSUCKITOUT - Poison doesn't affect you

ILOVETHISGAMEWHOMADEIT - Showw Credits

YOULOOKINATME - Unlimited Health

IFEELUNUSUAL - Unlimited Ammo