You can use one of the following cheat codes:

Code	Effect
Press Y, Up, Y, Right, Y, Down, Y, Left, Y, Up during game play	AA
Press Down(3), LB, Down(3), RB, Down(2) during game play	Enemies do not target you
Press Y, B, A, X, RB, Y, X, A, B, RB during game play. Note: This may need to be entered for each weapon	Full ammunition
Press LB, Up, RB, Up, LB(2), Up, RB(2), Up during game play	Invincibility
Press LB, Down, RB, Down, LB(2), Down, RB(2), Down during game play	Kill
Press Left(4), LB, Right(4), RB during game play	Level select
Press Up(3), LB, Up(3), RB, Up(2) during game play	No Clipping mode
Press Up(2), Down(2), Left, Right, Left, Right, B, A during game play to regain 25 points of health	Restore health