RolerBall
RolerBall. This gigantic RolerBall is simply awesome, potentially dangerous, but nevertheless awesome. Once inflated this behemoth stands about three metres high, and is rather like a spherical cushioned igloo. The idea, which sounds insane, is to put it at the top of a slope (we suggest a very gentle one with a long unobstructed run-off), strap yourself in, and then roll down the hill trying not to lose your lunch. Inside the centre shell are two harnesses, so you could have two people feeling the adrenalin rush, and probably the queasiness, together.
