Microsoft Arc Touch Mouse with BlueTrack Technology - Curve to Turn On, Flatten to Turn Off!
I happen to spend about 16 hours a day on the computer & I can vouch for this mouse. It's light, sensitive, durable, comfortable - all in all a very good buy.
(I bought it for about $80 in-flight duty free on lufthansa or BA about a year ago and I am still using it)
24h only at
http://lastcall.dailysteals.com/( I am not in any way affiliated with DailySteals )