I've always loved wind-up toys. Back when I was a kid I had tons of the little wind-up animals and robots (most made by the manufacturer Tomy.) Penguins and Geese and Chicks and R2-D2 knockoffs - they were all fun and probably inexpensive which would explain why my Mom bought me so many over the years.
Nowadays if I find them at the flea market or a garage sale and they 1) work 2) aren't broken and 3) are cheap, I will usually bring them home for my little intern to play with. Unfortunately when I do find them they rarely work, and if they do they are rarely cheap or unbroken. The following three are recent exceptions (well, for the most part:)
I'm pretty sure I had a hopping Woodstock when I was a kid, I'll have to be on the lookout for him to complete the quartet!