This is a case I designed for the iPhone 4, I have only made with PLA. Case is very rigid unlike a lot of cases found on here. The design is similar to http://www.thingiverse.com/thing:67704 but in my opinion, I have added some better features and a couple chamfers to make the phone easier to get in and out of the case. I also uploaded the Autodesk Inventor .IPT file and the .STEP so you can change it if you'd like.

I even tested the case by dropping it with my phone in it from 6 feet onto concrete. The case only had 1 minor crack on the corner it landed on.