Valve is currently testing Half-Life 2: Deathmatch on the Linux Steam client. So far it runs flawlessly minus a few graphical (mostly stutter) glitches. Grab a copy for $4.99 in the Steam store.
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Fast multiplayer action set in the Half-Life 2 universe! HL2’s physics adds a new dimension to deathmatch play. Play straight deathmatch or try Combine vs. Resistance teamplay. Toss a toilet at your friend today!
Website: store.steampowered.com