The Blender 3D open source community is highlighting the power of their software by producing Apricot, an open source Blender game. By the looks of the various sample videos (see one below), it shows a lot of promise.
What makes this even more interesting is the availability of a playable demo. Hurry, download it and see how awesome and powerful Blender is.
Whilst this isn't exactly about Linux, it is software that runs beautifully ON Linux! :P