I don't know if this really qualifies as a good application or not, but it's something that I couldn't resist.
My wife and son came home one day last summer with slurpees and they bought these straws with clear plastic skulls, about the size of a walnut, near the tops. Inside the skulls were blue plastic brains. Pretty neat straws really. But I immediately thought about my son's broken fire truck sitting downstairs on my workbench...with two perfectly good LED emergency lights. So I remove the LED's, drill a hole through each eye in my straw-skull, insert LED's, and tape on two AA cells. I wired it all up and left a little piece of metal across the ends of the two cells...not quite touching so that if you push on it, it makes contact. When contact is made the LED's light up and my straw-skull has scary red demon eyes.
Maybe I'll grow up someday, but I doubt it.
