Last year saw the release of the first Unreal Engine 3 game with a native Linux client. UE3 has been around for years but the Linux port of Unreal Tournament 3 that was done by Ryan Gordon was never released. Finally in 2012 we saw the first Unreal Engine 3 title running on Linux.
Nordic Games shared this morning that they're porting their UE3 shooter game to Linux and Mac OS X. The Linux version of Painkiller Hell & Damnation is expected to be released in April or May.
Painkiller Hell & Damnation was released last October for the PC as the sequel/remake to the very popular Painkiller game from 2004. This first person shooter is powered by a fairly vanilla Unreal Engine 3. The announcement of the forthcoming Linux port was announced today at PainkillerGame.com.
Yes, this game is distributed via Valve's Steam client.
It still looks like 2013 will be the year of Linux gaming.