Enter at the title screen: Up, Black, B, Left, Y, X , White, L, B , R.
Add weapons option when paused
Enter at the title screen: UP, DOWN, LEFT, RIGHT, B, X, UP, DOWN, LEFT, RIGHT, B, X.
All Missions and Pictures
Enter at the title screen: WHITE, BLACK, L, R, L, WHITE, WHITE, BLACK, L, R, R, BLACK.
Cowboy Cutscenes
If you enter your name at the beginning of the game as "COWBOY", your character will have a cowboy hat on in all cutscenes.
God Mode
Enter at the title screen: click Right Thumbstick, Click Left Thumbstick, RIGHT, LEFT, L, R, Click Right Thumbstick, Click Left Thumbstick, RIGHT, LEFT, L, R.
Infinite Ammo
Enter at the title screen: BLACK, R, Y, WHITE, L, UP, BLACK, R, Y, WHITE, L, UP.