Some American rocket-scientists have gone and made themselves a rocket-powered bike.
Well, two rocket-powered bikes actually. The first one - with a 35-pound-thrust rocket engine bolted on - "didn't kill anyone", so they got another bike and mounted a 200-pound-thrust engine on the back. It can do 0 to 60mph in 5 seconds, which presumably makes it great in a straight line but hopeless at cornering.
Personally, I don't think I'd like anything capable of that amount of thrust anywhere near my arse...