Sinistar
Sinistar is an Atari 2600 version of the 1983 Williams arcade game, programmed for Atari by Lew Harp in 1984. It is a prototype that was never released. Atari squeezed the arcade game into an 8K cartridge, and the last known version was close to finished, but the game was shelved during the video game crash. You can play it here in your browser.