Man's Best Friend
Everyone who travels with electronics knows what a pain it is to carry different power adaptors and finding outlets to plug them into makes matters even worse. There is an obvious need for a low-power standard. The ubiquitous USB interface is the closest thing we have to solving the problem.
Certainly, useful devices like cell phones, headsets, memory sticks and cameras use USB now for power, but this smart standard has spawned an impressive array of useless devices as well.
The folks at EverythingUSB list gadgets like the Seat Heating Pad, Ghost Radar, Noodle Strainer, Vacuum Cleaner, and Ashtray. ThinkGeek is selling Rocket Launcher, Snowman, Holiday Tree, Aquarium, Mug Warmer, and Lava Lamp. We've used our CoolIT USB beer coolers in the past with great success.
The silliest use of USB has to be the humping dog, it uses up your batteries and what do you have to show for it - dirty pants and a dead laptop battery?