Photographic evidence

Buy a cheap auto focus camera with a flash and a self-timer. Set the timer and the game begins. Each player must hold the camera at arm's length and point it at themselves very briefly, before passing it on to their left. Keep going and until eventually the camera will go off with a flash, and much laughter. The loser must down their drink, before the next round commences. The shots you get back will be very amusing. Don't bank on your camera surviving the game for long!