After years with wireless mice, I switched back to a wired one. I'm using the Razer DeathAdder. I am happy with it and I never have to worry about it being charged.

http://www.razerzone.com/p-69-razer-...ing-mouse.aspx

Mac version:

http://www.razerzone.com/p-124-razer...ing-mouse.aspx

For travel, I have one of the original MS Wireless Notebook mice. It has the click scroll wheel and uses a single AA which lasts for months.

I refuse to purchase a mouse without the clicking wheel since I use it for page at a time scrolling by default (Ctrl+wheel for small increments with the FlyWheel utility).