Press the [SHIFT] and the [@] key or the [~] key (on some systems) to make the console window appear. Then type any of the following codes:

Code - Result:

SISSY - Enable Cheats
Alamode - God Mode
PackNHeat A- dd Destructive Weapons
PayLoad - Add Ammo
IAmSoLame - All Weapons, Ammo, Invisibility
PiggyTreats - Lots of Doughnuts
JewsForJesus - Lots of Cash
BoyAndHisDog - Lots of Dog Treats
Jones - Lots of Health Pipes
SwimWithFishes - All Radar Related Items
FireInYourHole - Rocket Cameras
IAmTheOne - Lots of Catnip
LotsAPussy - Lots of Cats
BlockMyAss - Body Armor
SmackDatAss - Gimp Suit
IAmTheLaw - Cop Clothes
Healthful - Full Health & 4 Medkits
Whatchutalkinbout - Bystanders Into Gary Coleman
Osama - Bystanders Into Fanatics
RockinCats - Cats on Guns
DokkinCats - Removes Cat Repeating Guns
IFeelFree - No Clipping Mode
LikeABirdy - Fly Mode
Slowmo # - Set Speed to #