Galaxian 3 Codes -

Debug mode:
Press L1, R2, R1, L2, Up, Down, Up, Down when the Namco logo flies on the screen.

Ghost player:
Enter the play record screen and enable that feature. Start a game and play as far as possible. Then, enter the gunner battle option and press Right(2) to select "Ghost". Start another game to have your self as a partner.