The obligatory puzzle cube I created using Fusion... Not overly challenging, but an intriguing gadget which will look nicer when using multiple colours for the parts.

Sliding faces have 0.1 mm clearance each (0.2 mm gap size), which worked for me when printing at an overall size of 50 mm and a layer height of 0.2 mm (printed with slicer at 50 mm/s and Ender speed increased to 200%).