Otterbox Defender - It's strong, doesn't creak and gives great protection. However, some would call it big. That doesn't bother me. I find the S3 way too skinny without the case on it and difficult to use because of the thinness With the case, I have something to hold onto that doesn't slip from my grasp.
I also find the power button and volume buttons too easy to press without the Defender case on it. With the case, the buttons need a little more pressure to work,which I find perfect. I don't get any accidental volume presses when I'm trying to dim the screen with a momentary power button press.