Armor and Health
Enter L1, R1, circle, L1, R1, X, L1, R1 to refill your armor at any time in the game. For a health refill, enter L1, R1, X, L1, R1, Square, L1, R1. Use these codes to prevent your character from ever seeing the "Wasted" screen.
Cash Flow
Avoid the need to perform missions for cash by entering L1, R1, Triangle, L1, R1, Circle, L1, R1. This code gives you $250,000. Repeat it as many time as you wish.
Weather
To alter the weather of Liberty City you can enter a selection of codes. Create rain by inputting Up, Down, Square, Up, Down, Circle, L1, R1. Create a foggy day by inputting Up, Down, Triangle, Up, Down, X, L1, R1. Bring the citizens a sunny day by entering L1, L1, Circle, R1, R1, Square, Triangle, X.
The Tank
Rather than driving around in a car, opt for the Rhino Tank by entering L1, L1, Left, L1, L1, Right, Triangle, Circle. The Rhino will appear in front of you. For a less conspicuous vehicle, enter Triangle, Circle, Down, Triangle, Circle, Up, L1, L1 to create the Trashmaster, a large garbage truck.
Weapons
Cheat your way into receiving three sets of weapons. Unlock set one by entering Up, Square, Square, Down, Left, Square, Square, Right. Enter Up, Circle, Circle, Down, Left, Circle, Circle Right to obtain set two. Add set three to your arsenal by entering Up, X, X, Down, Left, X, X, Right.
Wanted Level
To raise your wanted level without causing any destruction, enter L1, R1, Square, L1, R1, Triangle, L1, R1. To prevent yourself from seeing the wanted level rise, enter L1, L1, Triangle, R1, R1, X, Square, Circle.
Random Destruction
If you find yourself stuck, you can commit suicide when you enter L1, Down, Left, R1, X, Circle, Up, Triangle. If you just need to clear a path, enter L1, L1, Left, L1, L1, Right, X, Square to blow up every car in the city.