Pause the game and enter any one of these codes at the map screen:

All guns: Y, A, A, Y, X, B, B, X, A, X, B, Y
Decrease Riot Level: Y, B, A, X, Y, B, A, X, DOWN
Increase Riot Level: Y, B, A, X, Y, B, A, X, UP
Infinite Ammo: Y, X, X, B, Y, X, X, B
Money Cheat: Y, B, Y, B, X, A, X, A, DOWN, UP
Restore Health: X, B, X, B, X, B, X, B
Tornado: Y, B, A, X, X, A, B, Y