There's a new game on kickstarter looking for $40,000 in funding called FORCED. They claim it's like Diablo meets Left4Dead. It's coop arena combat. It's being made with the Unity3D engine and will have full Linux support. I donated $15 cuz that's the amount to donate to ensure a "free" digital download (though of course somebody pointed out that since I paid $15, technically it's not "free," ha. ha.) once it's finished (sometime in February they claim).
Go check it out! They've got 14 days left to meet their goal and they're halfway there.