TU298LL/A iPod touch 2G Air Jacket (black)
Not sure you'll find a slimmer case than this. The matte finish is comfortable in the hand, and does not show fingerprints much.  Of course, a very small portion of the front chrome bezel is left exposed, and it clearly does not provide anywhere near the same level of drop protection as other more bulky cases.      I really like the crystal film screen protector that comes with this as well.  Very durable, though it does not extend across the entire screen, leaving a mm or two exposed around all the edges. 