If the VR is good enough to make your brain fall for the illusion, paintball and laser tag are just a few of the many things you could implement. Imagine paintball, with rocket launchers and zombies and fire and bottomless pits with no risk of injury. I would definitely pay to do that with my friends in a laser-tag type setting.
Not to mention the global reach of such technologies. Imagine XBox Live with laser tag/VR FPS and people from all over the world could play. There could be massive tournaments and competitions.
After thinking about it I think the best game play would be in a trampoline cage.