Mission select:
While youare at the Title Screen, press X, L2, Triangle, R2, Select.

Quick missions:
While youare at the Title Screen, press R1, L1, L1, R1, R1, R1.

Special features:
While youare at the Title Screen, press L1, L2, R1, R2, X, Select.

Invincibility:
Pause the game and press L1, R2, L2, R1, Select.