The Pak-Lite is a LED light that simply clips on to the top of a 9V battery. They claim that in low power mode, it lasted for a year continuously on a lithium 9V battery. Pretty impressive. 9V batteries may be less convenient than the more standard AA size, but in addition to being able to give your tongue a good jolt, they are conveniently shaped to form a flashlight handle. They suggest using your old smoke detector batteries, which probably have some juice left in them.
Now I’m waiting for a good LED light for my home that charges via solar during the day, and gives off light like a candle at night. Nothing to plug in, no cables, no chargers…cool.