Boy, this kinda came out of the blue. A talented developer has taken Doom 3 and made it compatible with VR headsets. You'll need Doom 3 BFG, although the non-BFG version might work. Unzip the files to a directory, copy the game assets over, fire it up, and grab your shotgun.
There's a few modes that you can play in, like seated or standing. If you have the HTC Vive or a Razer Hydra, you can even use them to aim and fire your weapon, which will be decoupled from your view.
The game does use the traditional FPS movement feature, so a lot of you might get sick playing it. Most people can get used to it after a few sessions, so if you're really wanting to play a game that doesn't use teleportation, but a walking mode, then I suggest sticking to it and building up your VR legs by playing a little bit each day. Eventually, you should be able to play without feeling nauseous.