I have kept to my guns about what to stock for batteries for well over a decade now. I pick up economy packs of AAA, AA, C and D as well as 9v transistor batts. I try to avoid owning anything that takes something other than those standards. The ones I stock are fairly universal, and can be had in everything from cheap industrial style to Lithium Ion. If I had to use a device that wouldn't accomodate one of these size batteries, I would grab an external battery holder and kluge it onto the device so I could use one of the standards.

I wouldn't have anything to do with 9v except that the CO and smoke detectors have to have them, and kluging those devices could get me in a lot of trouble if something went wrong (tampering with such safety devices is a no-no). As yet, there hasn't been anything I couldn't do without or find a substitute for that wouldn't take one of the standards, excpet that G2 Nitrolon flashlight I bought on an impulse in Baghdad.