This really depends on how you "carry" you phone. Do you like it in your pocket, or on your belt?
I prefer mine in my pocket. I don't want to look like I'm trying to prove something and I don't like the feel of it hanging off of me. I purchased this Incase. It works great, feels good to the touch, has good grip, easy to put in pocket, and gives you 100 percent functionality of your phone. Also, it has a cool design to give your phone some flavor.
There are a lot of options out there. Just have to decide what you're looking for first. All cases have their own distinct advantages.
All the cases from senacases.com are nice. I bought my wife the black alligator case with the magnetic flip cover the week after I bought her phone and 6 months later her phone looks brand new....Kinda of pricey but well worth it.....http://www.senacases.com
While I do love my black Agent 18 look into another case, the Agent 18 scratched the chrome bezel and the back of my iPhone. Or you can get it but when you do put it on your iPhone wipe the phone clean.