AAA, AA, C, or D-sized batteries can all be accommodated at the same time, and while the flashlight's LED bulb won't be blinding when relying on a single AAA, it will still provide ample light to get around.
To keep the Any Battery Light cheap—just $24 when it goes on sale in January—the flashlight's lacking the requisite hardware to use the different-sized batteries all at the same time. Instead, a rotating power switch lets you choose which battery you want to use. But with every battery slot filled, Panasonic claims the flashlight will run for up to 86 hours straight, making it a must-have for any emergency kit. More here.