If you like first-person shooters, you'll love Sauerbraten. This open source game might not have the visual finesse of other FPSes, but what it lacks in the graphics department, Sauerbraten more than makes up for with its various single and multiplayer modes, including an experimental role-playing game mode, and a unique WYSIWYG in-game map editor. Sauerbraten blends the best of FPSes like Quake and Max Payne to give you a unique gaming experience.
This verdict isn't a surprise since Sauerbraten has a very good pedigree. It's based on the redesigned Cube game engine developed by well-known Dutch programmer Wouter van Oortmerssen, who is a professor of software development and has written a few programming languages. The latest edition of Sauerbraten, which includes Capture The Flag gameplay and therefore called the CTF Edition, was released in June and runs on Linux, Windows, and Mac OS X.