For the really paranoid types: the Duck Image Number-Lock USB Flash Drive. This flash drives uses an old school technology for a bit of a new-school security. The cap of the flash drive is held on and locked via a rotating number dial, similar to the one you used to (or still) use to secure your huffy bicycle. Once the cap is unlocked and the flash drive is plugged in a password is required before being able to access the data. Duck Image has had this conceptual design around for a while, but come on, doesn't anyone want to jump on this idea? It would make ka-jillions! SanDisk? PNY? Sony?
Duck Image's Super Secure USB Drive Design [Everything USB]