Fish shaped gears.
I built this the other day from the weird gear plans at http://lisaboyer.com/Claytonsite/Claytonsite1.htm
If you need proof that the gears actually work, here's a quick video I made that has slow motion at the end: https://www.youtube.com/watch?v=zDz06S-S_TU
If you own a scroll saw these plans are fun to cut out and to watch as they turn. I want to do a post someday on these and hopefully I can get Clayton Boyer to allow me to share a template or two!