There are a ton of cases out there, but I spent forever looking for one that
1) Looked unique
2) Would preserve the resale value of the phone
3) Didn't take everything away from the design of the phone (otterbox)
I feel as though you almost do need a silicon/rubber element to the case if you want to really protect it from drops, but a purely rubber case isn't a very elegant look. I've had them in the past for other phones, but it seems like you do want to show of the phone a little more than that.
I almost got an xShot case or a Gorillamobile case as I would love to just snap it onto a tripod whenever I needed, but I didn't feel like these were enough drop protection. Too bad nobody has made a 2-stage case that integrates a silicon sublayer with a couple of 1/4 20" screw holes. The ones they make for this are just ugly.
I almost got one of the Oakley Hazzard cases, but there were no reviews of them. They seem decent and the material sounds interesting:
http://www.oakley.com/products/hazard-case-for-iphone-4/99135-001
(I think if they would have included a screen protector I would have grabbed it right away).
I finally decided on the DIY Case-mate Tough case. While it's not perfect from the youtube videos - it seems like a pretty good balance of protection and uniqueness - since I used the 20% of coupon code and then designed my own case, I felt like maybe it would stand out more than a regular case. It has an inner silicon shell and a harder outer cover that can be customized with your own artwork. Additionally, I think it's important with the 4S, that there's a little larger area for the camera and led flash, as possibly cases designed for the ip4 have smaller areas for this and could cause flash washout?
We'll see! Here's are renders of the designs I considered...
Here's a video review of the case (not mine):
http://www.youtube.com/watch?v=cbwt7KEDx08
We'll see how it turns out!