Cheat Menu:
Press Left, Right, L1, R1, Circle, Square, R2, L2 at the title screen.

Unlock It All:
At the main menu, press Left, Right, L1, R1, Circle, Square, R2, L2 If you entered the code right , you will hear a meow kind of sound. This unlocks all weapons in free patrol and all the other cars and stuff in the bonus items menu in the options menu.

All Starting Locations in Patrol Mode:
Press Down, Up, L2, L1, X, Triangle, R2, R1. You will hear a sound if it is done right. Do it at the main menu.

Level Select:
Press Down, Up, Left, Right, , Triangle, Circle, Square at the main menu . A sound will be heard if doen right.

GameSharks Codes

Infinite Health (Including Enemies) 
800707E4 2400 

Infinite Ammo 
8006B454 2400 

Unlock All Missions (Pursuit Mode) 
800FC0BA 0014 

Unlock All Missions (Single Mission Mode) 
800FC342 0014 

Unlock All Locations (Free Patrol Mode) 
800FC340 FFFF 

Unlock All Bonus Items 800FC344 FFFF 

Thanks to Revolution readers Joe Cekosh, rob ure, mike, Frans Jogchems and Zack Tucker!