I came across this super fun Chain Clock on Thingiverse today.
Wow, I dreamed of making exactly this very thing a few years ago! I even went and built one in the Phun 2d physics simulator (that is now Algodoo) What a blast that was! I highly recommend playing with that toy as well!
I wanted to make mine out of bike chain and cut steel but… well, there’s never enough time! It really gives me a smile that such a thing exists in the world!