I don't keep mine in a case. Unfortunately I was retarded one day and it finally smashed. I personally can't stand the cases, I got a brushed aluminium backplate and I still don't use a case, the iPhone just looks too good. I know I'm ignorant about the matter, but I don't really care.
But if you would like some minimal cases for your iPhone:
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I really like the Griffin Reveal but it's really just like an Apple bumper.