http://ioquake3.org/
Its an open-source 3d game engine, written in C and uses SDL.
It seems like a great candidate for a Dreamcast port, this engine would open up a lot of possibilities.
So, I am not experienced enough at programming, so I am curious what some of you current DC programmers think about the idea?
Screenshot of the engine in action:
http://ioquake3.org/images/screenshots/tremlinux.jpeg