While OS X Lion updates all of the multi-touch gestures available for Mac computers, but (at least for now) people who have PCs still need buttons on their mice. This mouse, called the X Mark I Lite, was recently released by Canon and comes with an integrated 10-digit calculator or numeric keypad (whichever you prefer)!
While this might seem an odd peripheral for some people, especially those that have both a plain old calculator and a mouse on their desks, the mouse can double as a numeric keypad. Most of today’s new, minimal keyboards eschew the numeric keypad, so this is really handy for bringing that back.
This mouse has Bluetooth connectivity and is made out of recycled materials from Canon copiers.
If you don’t like the layout of these buttons, you could always just ask Google or Wolfram Alpha to do your calculations for you (which is what I do).