I'm not too rough on my iDevices, but if you are, consider the Griffin Survivor iPhone case. At US$49.99 it costs more that most other cases, but it will likely protect your phone in dire circumstances that would compromise others.
Griffin claims the Survivor meets or exceeds US and UK military specs. In fact, it's really two cases. An inner plastic case surrounds your phone, hugging it closely. You can open the case with a handy slot that accepts the edge of a coin.
Then, you slip the inner case into a rubberized cocoon that adds thickness and protection. There is also a shield that protects the display. Every port is covered, so you should get good immunity to dust and moisture. The home button and volume controls operate with the phone in the case. All the other ports have a rubber flip-up cover. The front facing camera is exposed for using FaceTime, but is behind the glass shield. A removable belt clip allows you to carry the phone either horizontally or vertically.
Throwing caution to the wind, I dropped the phone a few times on a hard surface from 6 feet with no ill effects. I wasn't willing to risk anything more aggressive, but I get the point that the case is solid. You can view some torture tests of the case on the Griffin website that are truly impressive.