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 would compromise others.
Griffin claims the Survivor meets or exceeds U.S. and UK military specs. In fact, it's really 2 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 c
