A USB stick for proper performance. Beautiful, elegant and well made, the object is rather pleasant to watch / handle, and seems rather resistant to shocks. Having a USB key on his key ring is great: it was always with either. Many other key market can also do it but often the "silver chain" it rip => at least, the key will remain firmly on the keychain. For me, this is the main interest.
Finally, as has buy a USB key, so take an elegant and functional. This is well worth a few small euros more than the rest of the market. And little more: free online storage for 2 years 4GB Wuala (which I'm user) that's all benef '.