If you suffer from frosty fingers, this is a gadget you need for sure! When plugged in, the mouse heats up to a toasty 40-45°C (104-113°F) which is beautiful for those times when you've got to rush onto your PC for an ultra speedy blog post or urgent email and don't have time to heat up your digits before. Holding a cup of hot tea while typing is a pain, and a hazard to the health of your PC if you tend to be a bit of a klutz.
The USB Mouse with Infrared Heater ($22.99) switches off too, so once your fingers have defrosted, you can just disable the warming function.
Just a word of warning to anyone who's plagued with those bizarre urges to pee when their hands come in contact with warm water: this might not be the best gadget if you want to ensure uninterrupted productivity.