Build your own solar powered robots...then break 'em

A lot of people get some kind of weird pleasure in smashing up something they just created themselves, and that's exactly what you're supposed to do with these little battle robots. The Solar Powered Battle Symet comes as a complete kit, although it's not really for beginners, requiring you to solder together the circuit assembly.

Once you've built a couple, you can have backyard battles with your friends, secure in the knowledge that the fun won't stop until the sun goes down, or at least until you manage to bring down the hand of doom on your opponent.

The Solar Powered Battle Symet kits are available from Instructables for about $20 each.

Instructables, via Treehugger.com