Vega Strike - VS provides the backbone for a number of remix projects (like Pi Armada, Privateer Gemini Gold, and Parallel Universe). Explore space, build a trading empire, and blast your opponents to space dust. Plus, they just got their 'Super Ultra Cool Sound Systems' (SUCSS?) working last month.

Warsow - Warsow's developer credit Quakeworld, Quake CPMA, Jet Set Radio, and Speedball for inspiring aspects of their game, and it's a combination that really works. The game's fast pace and cell-shaded graphics work well together. Other cool features: dual firing modes (weak and strong) for weapons, wall jump, ramp slides, dashing, and dodging.

Widelands - If you enjoyed playing the Settlers games and haven't tried Widelands yet, now's the time. Lead your tribe to glory in single-player mode, or go multiplayer on your LAN or over the Internet. You and your friends can unite to form glorious new empires - or just try to kick the snot out of each other.

Wolfenstien: Enemy Territory - Mein Leben! Ok, so that was from the old, old Wolfenstein. The idea is the same: shoot all the bad guys or they'll shoot you (or blow you up). The links will take you to Planet Wolfenstein where you'll find downloads for all three OSes, map editors, source code, and more.

Yo Frankie! - Built on the Blender Game Engine, Yo Frankie is as good a 3d platformer as you'll find for free. There's lots of lighthearted action to enjoy, and new levels are constantly being developed by an enthusiastic community.