Hit ALT and \ at the same time to be able to enter these codes:
GARBLE          Garble cheat codes toggle
WILLNOTSTOP     Invincibility
ARNOLD          All weapons
SLUGS           All ammo
SURGERY         Full health
SUPERUZI        Get the Super UZI
TARGET          Enables targeting box on enemies
ILLBEBACK       Skips to next scene
NITROUS         Speeds up game
ICANTSEE        Shows viewscreen
WHOAMI          Shows your name
COUNTERS        Shows current co-ordinates
VERSION         Shows version
HELLO           Shows message: Hello?
SUPERTRACKER    Motion tracker (Version 1.01 only)