Japanese fidget rolling / spinning / wobbling toy.
This is a one-piece no-support no-assembly print at 100% infill. There are solid endcaps for weighting and the main body is hollow (see the cut-away view).
The OpenSCAD code is highly customizable. Among many size adjustments, you can also add holes where you can pause print and insert weights. Code uses and includes my Bezier library.
I printed in PLA (higher density than ABS) and superglued rubber circles cut from an old bicycle inner-tube on the ends.
Update 1: You can now print versions with polygonal sides. Depending on how you look at it, this makes the toy either more challenging or disappointing. It's just a lot harder to get to roll neatly with polygonal sides. Four sides is very difficult. But feel free to change the number of sides in the Customizer (it has 40 for a circle).
Update 2: No longer uses paths library.