I bought one for my bike and then one for my daughter, but have now found a great use for it. I've put it into "Mr Bones" my skeleton in an open casket that guards our front door on Halloween. I've placed it in his chest and now he has a beating heart. I also use fishing line so his arms move. He scares the little kids to where they don't come up to our porch. (I'm not that cruel, if I see they're really scared I show them the lines and tell them it's just a toy. I have kids too.)
The headlights that go with them will be used for back lighting some gory looking dolls, maybe also in flash mode. Those things are blinding and will outline the dolls pretty well.