A whistle-stop tour of the nominees.
Twelve activities for buzz-addicts that are so on-the-edge they frequently tip over it
Where to try it: Key West, Florida, with Jetpack Adventures
Here's your chance to live out all those futuristic James Bond fantasies. The jetpacks involved may not be burning rocket fuel - that would probably be rather dangerous - but the contraptions spurt out water at such a rate that they propel the harnessed-in user upwards. You're attached to a boat (from where the water is pumped in) and can steer yourself around with a fairly simple control system. The future of transportation has arrived, and it's all very silly.