Shadow Gunner

Invincibility
Triangle, O, O, Triangle, O, Square, X, X. 

Invisibility 
Square, Triangle, X, Square, Triangle, O, X, Triangle. 

Super Gun 
X, O, Triangle, X, X, O, X, Square. 

Top Down View 
Triangle, Triangle, X, X, Sqaure, O, Square, X. 

Level Select 
Square, X, Square, Triangle, X, Triangle, O, Square.

To access the cheat code screen hold down Select on the main menu screen and press Triangle three times..