Today I got to try the Lifestyle Smooth case from Ballistic. They have managed to create a case that is protective yet sleek enough to fit in a pocket. It is also customizable as you can swap out the bumper-car style corners with the included replacement parts, in assorted colors to complement the case itself, also available in a variety of colors.
Since the corners are likely to take the brunt of any damage due to dropping, those extra cushions offer a degree of confidence that most cases don't. The case itself adds very little bulk, so it could be an everyday case, hence the words Lifestyle and Smooth in the name.
The iPhone's glass is protected by a raised lip, which should help with most drops. The opening for the rear camera is perhaps too big, about the size of a dime, so there isn't a lot of protection there, but that's the tradeoff for the sleek design.