The meat and potatoes of "Tekken Tag Tournament" is the tag mode that allows you to hit the shoulder button to call in another previously chosen fighter to help you defeat your opponents.
That said, if you snagged yourself a Rift dev kit and have no intention of actually developing games with it, the upcoming UDK release also includes a "VR Mode" version of the software's sample Unreal Tournament game, as well as a summer version of the Epic Citadel demo we were shown at CES 2013.