I was waiting for a Steam sale to see if Doom 3 BFG Edition would be discounted because of a recent mod that made the game all the rage in the VR forums, but Bethesda has got you covered.
If you go to their store, you can grab the game for a low, low price of $6.66 (ha, ha). After you check out, you'll be given a Steam key. Pair that with the VR mod and be prepared for a brand new way to play the game.
As I mentioned before, there's a good chance you'll get a queasy playing the game, but if you can build your VR legs with some practice. After a little bit, there's a good chance you'll be able to play without feeling the need to vomit.
Word is that multiplayer mode works, but no co-op mode yet. The nice thing about Doom 3 is that the source code was released by iD so there could be some talented programmer that can get that into the game.