Galaxian 3 Debug mode
When the Namco logo flies on the screen, press L1, R2, R1, L2, Up, Down, Up, Down.
Ghost player
Go to the play record screen and enable that feature. Then, start a game and play as far as possible. Now enter the gunner battle option and press Right(2) to select “Ghost”. Start another game to have your self as a partner.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art.