I printed out an icosahedron recently, and coincidentally the holes in the faces were just the right size to trap the polishing media for WSF. When my icosahedron arrived it looked like this (two pieces already removed):
Apparently the polishers figured removing the 6mm diameter rods was not worth it, but a few minutes spent with some toothpicks and I got them out of their cage.
The icosahedron is just the core piece of this puzzle, which I have showed in a previous forum post. This version actually uses 10 different pieces and is consequently much more difficult.