Hi all!
Just wanted to mention a game that i've found to be incredibly fun: CUBE
CUBE is a free, open source, multi-platform (OpenGL), multi-player First Person Shooter that may look familiar to you Quake people. It is actively developed and has a good community of followers/supporters and dev's, the head-honcho being 'Wouter van Oortmerssen'. Compared with cutting-edge games that run on the new Unreal and Source engines, CUBE is step backward in time in many ways. However, what sets it apart from the more advanced engines is that it's just plain all-out fast, furious and FUN! Someone once defined CUBE as "You kill stuff. The end". It's a refreshing relief from the clutter and complicity of many commercial titles. Another trait worthy of mention is its in-game level editing capabilities. Level editing takes on a whole new dimension and is incredibly simple.
http://www.cubeengine.com/