I'm a big fan of EVE Online, and for the longest time, they used to have a native Linux port, and then they made it go away. I'd love to see it return, especially if tailored to SteamOS. SWTOR, STO, TERA and a couple of others would also be great to see, but by and large, a good chunk of the indie titles on Steam also work on Linux, so there isnt a real shortage. Also, plenty of Humble Bundle titles work natively under Linux as well, so this is also a good thing!