I got into contact juggling a decade or two ago. It is basically a form of juggling in which a clear or solid-colored ball stays in contact with your body to interesting effect. Think the Goblin King from the movie "Labyrinth".
It is rare enough that you don't meet many people that have seen it, and with enough of a learning curve that not many people that start ever really get anywhere with it.
Just takes a lot of boredom and lots of muscle memory. Not hard, per se, but unrewarding until you've put more time into than you'd think. A lot of skills within a week or so, you should have some sort of improvement to show for it. Not so much with contact juggling.
But once you've gotten ok at it, it kinda looks like magic.