The Otterboxes are definitely always a pretty valid option when it comes to cases, but sometimes they do add quite a bit of bulk to the phone. I was just searching around and fell upon these Diztronics. Seem to be pretty decent/ Amazon.com: Diztronic Matte Back Black Flexible TPU Case for Motorla Droid RAZR HD (Verizon - NOT FOR MAXX HD) [Diztronic Retail Packaging]: Cell Phones & Accessories
I love my incipio case i got from Amazon. It doesn't add much bulk and its two layers of protection.