Launched today with Humble Indie Bundle 7 was Dungeon Defenders for Linux. Dungeon Defenders is a tower defense / action RPG originally released for the PC in 2011. What makes this game noteworthy is that it was developed on Unreal Engine 3 and now there's a native Linux port.
Ryan Gordon confirmed today via Twitter that he's responsible for this Linux port of the first UE3 title. It's also interesting as he's using SDL 2.0 for the port. "Dungeon Defenders is an Unreal Engine 3 game on Linux, and it's the first thing I've shipped with SDL 2.0!"
Ryan Gordon ported Unreal Engine 3 to Linux years ago but ultimately was never permitted to release the Unreal Tournament 3 Linux client... Hopefully going into 2013 we'll see more Unreal Engine 3 games being released natively for Linux to compete with Valve's Source Engine and Unigine Corp's Unigine Engine.