In FaceOff Paintball you can use your head movements to duck in and out of cover, whilst you pick off the other paintballers. It features a head-driven handy-cam effect to make you feel more immersed in the game and an online leaderboard that updates in-game as you play. The tracking works using a conventional web camera, so there's no need to go and buy any specialised equipment. FaceOff Paintball can be freely downloaded today from: torbensko.com/faceoff
This seems like a very great game. If you could join Valve, you would be able to improve their games greatly.