Glow Graffiti. This magical "light painting" by rAndom is powered with UV light that lets you write and stencil pictures to create your very own glowing graffiti.
"It's like very complicated vandalism except much prettier and you won't get nicked by the police doing it. This really is a gadget of mind-boggling genius, perfect for parties (or if your nocturnal) and will have your friends intrigued for hours to how it all works. " [Via]