The original Magic Mouse. You know how it works and what it is. This one is $20 and comes with two AA batteries.
The Magic Mouse laser tracking engine provides a smooth, consistent experience across more surfaces than a traditional optical tracking system. Magic Mouse uses Bluetooth wireless capabilities to create a clean, cable-free desk top and its secure wireless connection works from up to 10 meters away. To extend battery performance, Magic Mouse includes an advanced power management system that works with Mac OS® X to automatically switch to low power modes during periods of inactivity. The wireless Magic Mouse is powered by two AA batteries