I just got a new Microsoft arc mouse and I really like it. I'm down in New Orleans this week for TechEd USA so using it on random surfaces at the event and in my hotel and it's been working great. I also like how the wireless works when presenting, unlike my previous mouse which would get overloaded with all the attendeed WIFI traffic making it unusable when presenting. The design is very appealing to me with the magnetic hold for the transceiver and the steel hinge to close it which also turns it off.

http://www.microsoft.com/hardware/mouseandkeyboard/productdetails.aspx?pid=112

My new favourite travel mouse. My last favourite was this one but I would not use that in my office because it's too small.