A Jesse Pinkman lithophane. It becomes a very high-detail image once you shine a light behind it, whether it's your ceiling lamp or you've put it on an outside-facing window (during the daytime, at least). 

I haven't gotten around to printing this one yet but there shouldn't be any problems considering it was made with the same process as the others. 

This works best with white filament, I wouldn't print it in any other color. It is printed in 0.1mm layer height for maximum image fidelity.