Making Arduboy mockups of classic Commodore games is great way to spend an evening. Dicky's Diamonds was a game published in 1983 by B. O'Shaugnessy for the Commodore 64. The game scales down handsomely to the Arduboy's scale and 1-bittyness.
BC's Quest for Tires is another favorite I can enjoy on the Commodore 64, Colecovision, and the Atari 8-bit. I am really happy with how my Arduboy mock-up turned out.