I love this iPhone case. The phone fits perfectly, there’s a nice cut-away where the buttons are, and the power button on the top of the phone has a spring-loaded 3D-printed part that makes it very responsive, with nice tactile feedback. The backside of the case has a set of working gears and a geneva mechanism (lower right of the photo). The main part of the case is printed in two pieces, and the gears and pins are printed separately. Then a little super glue here and there, and everything works smoothly. I didn’t even have to clean up the parts at all. Everything came straight off the print bed and fit together perfectly.
The model for this case can be found here: http://www.thingiverse.com/thing:79606 (model credit: Brandon Watt)