M.U.S.H.A.

Level select:
Reset the Genesis ten times, then hold Down/Left at the title screen.
A level selection entry will appear on the options screen.

Full power guns:
Pause game play and press B(2), C, B(2), C, Up, Down, A.
Note: This code may only be enabled once per game.

Secret options:
Pause game play and press Up(3), Down(4), Left(3), Right(3), C(2), B, A.
A total of 20 options will be available.
Note: This code may only be enabled once per game.

Five additional lives:
Pause game play and press Right, Down, Right, Down, Left, Up, Left, Up, B, C, A.
Note: This code may only be enabled once per game.