My DH has one by Ballistic - it is waterproof as well as shockproof. He works in a FIFO job and is constantly in either very dusty or very wet environments, so his phone needed good protection. The Ballistic case has completely protected his iPhone and still looks like new. The only down side is that it is a little bulky and was a bit expensive.
I use a leather wallet type of phone case. I'm on the second one now, because one of my dogs decided to take my phone outside and use it as a chew toy (I have Siberian Huskies, so very big teeth!). My phone still looks brand new and the only damage done was to the case. Having said that, I don't think they had it out there too long!
I continued to use the chewed up case until it fell apart this week. I am now using DH's old case which was the same as mine.
Edited by Gioiello, 20 November 2012 - 09:29 AM.