Grand Theft Auto

Enter the following at the Enter Name Screen:
nineinarow       All Levels and Cities
itsgallus        Same as Above
superwell        Same as Above
itcouldbeyou     Score increase by 999999999
suckmyrocket     All of the weapons, armor, and get out of jail card.
iamgarypenn      Enable Extra Offensive Language Mode
iamnotgarypenn   Disable Extra Offensive Language Mode
itstantrum       Unlimited lives
6031769          Same as Above
heartofgold      View All Cutscenes
hatemachine      Multiplier x 10
iamthelaw        No police presence
stevesmates      Same as Above
porkcharsui      Debug
buckfast         Press * on the keypad for all weapons, again for reload!
callmenigel      Same as Above

Easy Money:
Put a lot of cars in a row next to each other, very close together. Make sure you clean your car after every fourth one so the cops leave you alone. After you've got about 20 cars in a row, blow up the first one in line and walk along with the explosions to see your cash score go sky high!