Hmmm... Descent, modernised a bit. I'd prefer if it didn't have the self-leveling and the levels were less 2.5D, with mostly flat layout with levels. Something like an abandoned space station in zero gravity, no "up" direction, tunnels heading off in all angles, etc. It's a bit too much like a floaty Unreal Tournament the way it is now.
Then I could finally use my SpaceNavigator as a controller