After a bout of nostalgia involving the Quake II railgun, I decided to implement support for the Oculus Rift in Quake II for fun. Originally forked from KMQuake II, Quake II VR has developed into a highly modernized implementation of Quake II that features low-latency input and rendering, OpenAL audio support complete with HRTFs, sRGB color profile output, post-processing effects, and game pad support. It has served as a testbed for research into simulation sickness and incorporates features such as HUD counter-rotation to minimize it's impact on users.
Quake II VR natively supports the Oculus Rift, any SteamVR compatible HMD, and will be updated to support future HMDs as they become available. Source code and download links are available on GitHub.
See also Polygon's writeup: Free mod turns Quake 2 into a VR masterpiece