My favorite case is the Incepio SILICRYLIC case Incipio HTC ThunderBolt SILICRYLIC Hard Shell Case with Silicone Core, HTC Thunderbolt Cases, HTC Thunderbolt Soft Shell Case, HTC Thunderbolt Hard Shell Case, HTC Thunderbolt Carrying Cases, HTC Thunderbolt Premium Cases
Check the link above for pictures and color options.
I have used Incepio cases on my Incredible, DX2 and now my Thunderbolt. It offers great drop protection, nice feel/grip, prefect fit and lifetime warranty.
The only con is that is isn't the easiest to take on and off. I wouldn't recommend it if you like to pop in a spare battery often. They also make another case called the Edge, that is two pieces that slide together, that might be easier to remove nightly....
Best part was that it only cost me $4.09.
Verizon has this case on clearance for 4.99 right now, if you can find a store that has it is stock. They cost $15-$20 on eBay/amazon.