Batman & Robin

Small characters:
Highlight the "Exit" selection on the options screen and press [Left, Right(2), Down, Right, Left, Right, Left(2),Right, Down] four times and begin game play.

Thirty lives:
Press C, Left, Down, B, Right at the main menu.

Unlimited lives:
Press Left, Right, Up, Down, Left, Right, Up, Down, Left, Right, Up, Down at the title screen.

Unlimited weapons:
Press Up, Left, Down, A, C, D at the player selection screen.

View ending sequence:
Press B, D, B, D, B, D at the main menu.

Sound test:
Enable the "View ending sequence" code. Press Left + C during the ending sequence to pause. Press B, C, D, or the D-pad to hear different sounds.