Invincibility for you only:
(B)+(B)+(X)+(A)
-----------------
Invincibility for your team:
(B)+(B)+(X)+(B)
-----------------
Refill ammo:
(B)+(B)+(X)+(X)
-----------------
Automatic win:
(B)+(B)+(X)+(Y)
To enter these go to the enter cheats option at the pause menu and enter them.