Press pause, then press up, down, right, left, square, square, square.

Go to item screen and hold R1 and L1 and press up, square, square, left, square, square, down, square, square, right, square, square.

Type all of these cheats in at the mission select screen

All story mode missions:
L1 R1 L2 R2 left square L3 R3

All multiplayer mode missions:
L1 R1 L2 R2 left L3 R3

All mssion layouts:
R3 L3 R2 L2 R1 L1

Increase Score:

Pause the game and hold down L1+R1 and press Right(2),Left(2) on controller two.This will add 100 points to your score.