Three button optical mouse. Bought it from pishop.us.
- Can be used with any computer. No firmware or software needed.
- Buttons are non-programmable.
- The USB cord is only about 18 inches long, so is best as a travel mouse you can connect to a laptop or a keyboard with its own USB ports.
More info:
https://www.raspberrypi.org/products/raspberry-pi-mouse/