A fidget spinner built around herringbone (chevron) gearing instead of a plain bearing. The angled, self-aligning tooth profile gives it a smoother, quieter spin than a straight-cut gear would, and it's a fun small print to show off gear geometry rather than just a bearing in a 3D-printed shell.
Credit & Copyright: Processing - Robert Gendler, Roberto Colombari; Data - Hubble Tarantula Treasury, European Southern Observatory