I've got an iPod nano, and I'll admit that it almost never, ever leaves its case. While not everyone is as scratch-phobic as I am, I know that I'm not alone. Check out the iTank
cases by YoTank. Formed from a single piece of machined aluminum, the iTank nano weighs 3 oz., costs $45US and all but guarantees that you will be pulled aside at the security checkpoint in your local airport. iTank cases are also available for the iPod mini and iPod with video with a polished aluminum finish (black coming soon).
If you don't feel safe with this thing on your iPod, you never will.
[Via the Your Tech Weblog