Otterbox all the way. I chose the Commuter version ($35), as I found the Defender to be a bit bulky, and I didn't need the belt clip it comes with. It also comes with a screen protector which works well and is not noticeable at all when the screen is on, but becomes visible when the screen is off. It's also prone to collecting your finger smudges, but so are all of them it seems.
And if you don't mind me suggesting, go ahead and root your phone. You can still get the ICS update from HTC as long as your backup the bloatware and reinstall it when it's time to update. Even if you delete it outright, there are still methods to return your phone to stock.