Thexder (NES)

Thexder is a combination shooter/platformer game, oddly behaving like a roguelike game with tile-based movement and enemy AI. You can transform into "ship mode" and fly around, or you can transform into "robot mode" and run/jump, complete with gravity. Bullets are automatically-aimed to enemies, which is a neat feature.

Credits
Thexder contains a hidden credits screen. Moto Kanayama's name glows the same blue as the title screen on it. To access it you must enter Up, Right, Down, Left, Up, Right, Down, Left, Up, Left, Down, Right, Up, Right, Down, Left, Up, Right, Down, Left, Up, Right, Down, Left, Up. In doing so, you must hit each of the diagonals in between, so that you hold the next direction before releasing the first direction. An alternate way of looking at it is to, starting with Up, do a 720 clockwise, a 360 counterclockwise, and another 720 clockwise.

"Ending"
Assuming you manage to beat 99 levels of Thexder (or cheat; set RAM address to  and beat a stage) the game will display this screen forever, scrolling downwards slowly.

For some odd reason, it can also be accessed via a somewhat complex series of button codes. Power the console on, then on controller 1 hold Left + A, press Reset, release the buttons, hold Right + A, press Reset, release the buttons, hold Up + A, press Reset, release the buttons, hold Down + A, press Reset, and finally hold Start then press Reset.