AA i believe, although i own few battery operated devices myself so i could be wrong... i've seen pretty few AAAs though in my time
Well then, there is the problem. The devices that people use are consuming too much energy. They are not efficient. Most small devices in the uk are AAA. My TV remote batteries last about, well so long it is not even worth getting worked up about. I have to say though digital cameras drink batteries like drunks drink cheap wine. If silver' wants a wireless mouse why does he not buy one that has a little stand to charge it up (when not in use). I've never heard of a mouse with batteries (Insert joke here).
What a really in-depth discussion about batteries... I had a digital camera that took batteries and I was changing batteries all the time, so I took it back and got one that was chargeable and it lasts and lasts... But still batteries are nice for some things...