Cheat List:
Open your Hitman2.ini in the Hitman2 directory in a text editor and add "EnableCheats 1" without quotations right below EnableConsole.
You can activate the following cheats by typing them in the game while playing.

IOIRULEZ or IOIRULEY - God Mode on/off
IOIGIVES - All Weapons and Items
IOIHITLEIF - Health
IOISLO - Slow motion on/off
IOIER - Bomb Mode on/off
IOIHITALI - Ali Mode on/off
IOILEPOW - Special attack Mode on/off
IOIGRV - The force of gravity Mode on/off
IOINGUN - Nail rifle Mode on/off
IOIPOWER - Mega Power
NOTE: If you have a U.S. keyboard, just type IOIRULEZ. On European keyboards the Z and Y change place so you have to type IOIRULEY.

NOTE: Make sure you don't enter the cheats too fast. Type them more or less slow.