Crayon Physics Deluxe -- crafted a low-res (in fact, it's 32 x 24) shooter that pits a ship against invading aliens. Oh, and he made the entire thing out of Post-it Notes.
Download Post I.T. Shooter right now and see for yourself, and then feel free to wonder why anyone ever makes a sequel in a world as rife with possibility as ours.
[Via Robert Ashley]