If you want to protect your shiny iPhone 4 from the harshest conditions known to man, you may not have a better option than the Ballistic HC.
The $US50 case went through a myriad of tests for drop damage, vibration, extreme temperatures, humidity and dust to gain certification. It also has connector seals, water-resistant meshes and tough lenses to make sure that dust, dirt and other harmful materials don't damage your phone.
The cases are available for both iPhone 4s, some Blackberry Curve models and the HTC Evo. [Ballistic]