Stunt Cycle
Stunt Cycle is an unreleased Atari 2600 prototype from 1980, programmed by Bob Polaro. It converts one of Atari’s early dedicated home consoles, which was itself based on Atari’s Stunt Cycle arcade game: you build up speed on a motorcycle and jump a row of cars, Evel Knievel style. Atari never released it, but the prototype has survived and you can play it here in your browser.