Just got my iSkin evo4 Duo for my Classic 160 (Sienna on black). I like it a lot, very nice looking and seals up tight -- complete silicone wrap with a polycarbonate shell. The only negative (for me) is the flap that covers the headphones, it's a bit too tough for me to unplug so its coming off.
Note that with the thin silicone layer over the click wheel it becomes a bit less responsive, but that's going to be the case with any full-coverage case. You just need to use more of the finger pad than finger tip.
http://www.iskin.com/evo4_duallayer.html