The tandem unicycle: positively unbalanced
If you get the welding kit you asked Santa for, and you find the business of riding a normal unicycle a bit too easy, then why not take a leaf out of Corbin Dunn's book? He's created a tandem unicycle, which looks like a fiendishly difficult beast to ride.
Actually Corbin doesn't take the credit for inventing the contraption, which he says he saw at a mountain unicycling event in 2006 and decided to make one for himself. We came across his machine via the excellent Treehugger website, and as you can see from the vid below it is possible to ride the thing, at least for five yards or so. Obviously you need two riders of roughly the same weight to stop the whole thig seesawing over. In case you're wondering the chainring that's loose in the rear chain is a rudimentary tensioner, which "doesn’t work well enough", according to Corbin. "Does it fall out? Well, not yet, but I haven’t ridden it far enough"
You can read about the Tandem unicycle and get instructions for building your own at Corbin's Treehouse - let us know if you build one!