Alot of Opensource games would be cool to port. Freecraft, Super Methane Brothers, Planeshift, Xbill (lightgun support, of course), TuxRacer, Nethack (graphical version... forgot its name), and a whole slew of others. The biggest roadblock, of course, is DirectX; most games mentioned use OpenGL if they use a graphics acceleration engine at all. It can't be that hard to write an OpenGL engine for the XBox, right? (I'm not a coder, so it's likely I'm wrong).