Behold. This very satisfying, springy fidget. Easy and quick to print (under 60 minutes) with PLA. Though is more durable in PETG or even PCTG.

A friend of mine was working on an impact resistant air hockey mallet with a spring design - and I couldn't stop fidgeting with it. I modified it to make it a good fidget. 

The modifier around the spring is to help add weight to the outside - which will make the toy more satisfying to play with.

Just twist the knob back and forth to create a resonance. Printing this 25% larger will create a more satisfying experience at the cost of size, time, and filament.

It is fully print-in-place with no support or post processing.