Rivets on the UPS truck.

It takes quite a getting used to the iPhone's up-volume button as a shutter release over using the screen's button, but truly an enjoyable challenge once you've realized you've snapped tack sharp. Gripping vertically the phone with a middle and thumb, while pressing down with my index finger, works perfect. Had the iPhone 4S for two weeks now, and I've discovered the AE/AF Lock only today, a feature I've relied heavily on other cameras.