I recently completed a port a little while ago of the classic DOS game 'Sopwith' for the Gamecube.
For those of you who aren't aware, Sopwith is a little 2D freeware action game for the PC from back in the 80s that sort of received a bit of a cult following. In it, you fly a little biplane around blowing stuff up and trying not to get shot down (and also trying not to blow yourself up or crash. ).
Here's a link with the details which in turn has a link to the Google code page where you can download the source and executables if you're interested: