OP, I have killed 6 iPhones and today is the 5th anniversary of the iPhone. My most recent one has lasted the longest (year and a half) and I have dropped it a million times, it is used by my kids and overall lives a pretty rough life. The only case that has meet my criteria for function, looks and durability is the ones they sell at (of all places) mixed bag designs. They are available online at:
http://www.mixedbagdesigns.com/Spring-2012/Tech_7
They are "bouncy" if you drop the phone so they absorb the impact quite a bit. Mine is over a year old and still looks great, they have lots of patterns. I swear by them because I'm the sort of user that voids warranties.