Going from not juggling to juggling knives can be done in perhaps weekends.
Then, of course, you can do all the fancy multi-object patterns, but I've yet to see a reaction to three spinning knives surpased by five+ tennis balls. The five+ tennis balls are neat while the three (even just two) spinning knives is always a visceral holy shit please stop you're going to hurt someone.
edit: instruments, double jointedness
The primary key to any such interesting display is discretion. If everyone knows you play the piano, no one cares. If no one knows, and you hit Tchaikovsky's 1812 in the mall, everyone's shocked.
verdverm•53m ago
https://www.youtube.com/watch?v=gaDdrDdczO4
looks like he has some new ones