I couldn't find an unbalanced fidget spinner on Thingiverse that was what I was looking for, so I made my own. It features a "keyring" on one side and a bearing on the other of the central bearing. This imbalance allows the user to move it in many different ways (see additional photos).
0.2-0.25mm for both parts
You need to print out 1 frame and 4 bearing caps. I suggest laying out all four (spares too if desired) in your slicer to help with cooling.
Something about either the bearing cap model or the way Cura sliced it for me, but the jerk control fails to work, which makes the Y-axis timing belt on my Prusa i3 to skip. I found that setting the speed on the printer itself to 40% kept it from messing up. At 75% I could raise the speed up to 75% to finish the print a bit faster. The other options of course are to use someone else's cap designs or not to use caps at all, but I recommend using them for comfort and ease of use.
This design calls for two 608ZZ size* bearings, medium grit sandpaper and a pair of pliers.
1) Using a strip of medium grit sand paper, smooth out the round-edged hole for comfort.
2) Press each of the bearings into the other two holes, then use pliers to force the EDGES of the bearing flush with the frame. If you crush the metal between the inner and outer rings, the bearing may fail to spin properly.
3) Push the caps into the bearings. It should be a bit difficult, but if they don't quite fit, sand the edges of the triangles until they do.
*NOTE: I'm not quite sure how bearing sizing works (608 vs 608Z, etc.), so if you aren't sure either, this spinner is designed specifically for "608ZZ" bearings.
Here's an Amazon link to the ones I bought (they're pretty cheap, but they work way better than the ones I cannibalized from an old skateboard):