Go to the 'Map' screen during gameplay and turn Real Time off. If you then press Circle, Circle, Square, Circle, Triangle, X, X, Circle you will become invincible.
During gameplay press 'Select' to display the map, then enter the following codes followed by 'Select' to enable the corresponding effect. Note: you may have to press 'Select' repeatedly to return to the game.
Press L1, Circle(2), Square, Circle, Triangle, X(2), Circle.
Press L1, Triangle, X(2), Circle, X, Triangle, Square(2).
Press L1, X, Square, Triangle(2), X, Circle, Triangle, X.
Unlock ALL Weapons and Psionics
Press L1, Square, Triangle, Square(2), Circle, Square, Circle, Triangle.