I often check out lifehacker, and today they have a clever list of tricks to store on thumb drives. I love the USB key - you can wander into a prospect and have any number of tricks "up your sleeve" and ready to go on the USB key. Anything from special reports, to new product features and everything else you find useful at a customer site.
Top 10 USB Thumb Drive Tricks
What have I used them for? Importing customer data into demo systems, getting important hotfixes into live environments, storing great screenshots of impressive reports or data. The list is endless and you can fit it into your pocket, carry onto any customer site - goes where your laptop cannot, or should not be used!