Battery Conundrum.

I just bought a radio that uses 3 AA batteries, which I have installed because using it on batteries is useful for some things. But batteries tend to come packed in multiples of two and four. So I now have a left over battery that will sit in my drawer for the foreseeable future, since most of the things that use AA batteries around here use at least two at a time. Perhaps I should go out and try to find a penlight that use one AA.