Valve is currently testing Day of Defeat: Source on the Linux Steam client. So far it runs flawlessly and does not suffer from the mental load times plaguing Team Fortress 2. You can grab a copy for $9.99 in the steam store.
Test system:
- AMD FX 8150
- Nvidia GTX 560Ti 313 drivers
- Ubuntu 12.04 LTS 32-bit
About:
Day of Defeat: Source takes the classic gameplay of the original Day of Defeat and improves the experience with Source, the advanced engine technology Valve created for Half-Life 2. With this technology, DoD: Source offers state of the art graphics (including support for HDR lighting) in optimized versions of popular maps, plus redesigned sound and all new player, weapon, and world models.
Website: www.dayofdefeat.com