GizMac’s Titan Gear for the second-generation iPod nano isn’t really a case, per se, but rather several accessories for wearing your nano about your person. The kit includes an armband, a lanyard, a carabiner clip, and a belt clip, plus an adapter to attach any of them to the nano.
The Titan Gear system works as follows: attach the included nano holder to the accessory of your choice by aligning the holes in the holder to the small pegs on the attachment. Then slide the nano into the holder. If you want to use a different attachment, remove the nano holder from the accessory and repeat the process.
That’s how it works in theory. In practice, although I had little trouble attaching the nano holder to the accessories, I had a very frustrating time trying to get the holder off again. (The exception was the armband, which was flexible enough to allow me to bend it so the nano holder popped off.)
The plastic of the holders appears flimsy, but it’s surprisingly resilient; I couldn’t snap any of the pieces even after applying a fair amount of force. And the nano fits very firmly inside the holder — there’s little risk of it flying out. But the snug fit also means it takes some effort to get your nano in and out of the holder.