For a school project, I made my first mobile game in 48 hours. I spent a little bit of time tweaking it since then, but the bulk of it I did in a weekend. It's only for the Windows 7 Phone, so I won't bother giving a download link.
It's a very simple game. The player uses the phone's accelerometer to move the ball forward and to the sides. You dodge the pyramids or else suffer a speed penalty, and collect the hourglasses. Score is equal to distance in tiles of rows. That's it. I was hoping to get audio in the game before I attempt to put it on the market.