I really like how Logitech solves this problem with their Performance MX mouse. It takes a AA battery and includes a rechargeable AA battery. When the mouse's

I really like how Logitech solves this problem with their Performance MX mouse. It takes a AA battery and includes a rechargeable AA battery. When the mouse's battery runs low, you just connect the (included) micro-USB cable. The mouse recharges and can be used at the same time, albeit tethered. Once's it's charged, put the cable away and keep on working.