I acquired a Gakken 大人の科学 (Science for Adults) kit - this is a sort-of magazine/science construction kit for adults. They have lots of really cool kits, which are normally $50-100 purchased new through Kinokuniya, but I found this one listed on eBay for $10. This one is a Mini Strandbeest kit.

The original Strandbeests (Beach Beast) are massive PVC-pipe constructions that walk along beaches in the Netherlands. They were invented by Theo Jansen, and many examples of them can be found on his website here.

This miniature version was a pretty quick build, with most of the difficulty lying in careful coordination connecting the legs on to the crankshafts. It has 12 legs, arranged in 6 pairs. The most difficult and really only frustrating part of the build was at the very end - constructing the propeller. The metal rod that is supposed to affix the propeller to the model would not easily pass through the propeller, and the windmill blades do not like to stay attached to the propeller either. They are affixed with double-sided tape. It's possible that the kit is just old, and the tape is thus less effective than it would have been when first released. One of the blades did fly off during one of my tests and had to be retrieved and retaped.

That said, it is really magical when it walks. Highly recommend.