Wild Metal

Invincibility:
Press Y, Right, B, Left, X, Down during game play.

All weapons:
Press A(2), Right, Y, A, Right during game play.

Full health:
Press Down(2), A, X, B, X during game play.

Level skip:
Press Up, Right, B, Y, Down, Left during game play.

Speed boost:
Press Up, X, Down, B, A, Y during game play.
(Information from Cheat Machine)