A poor man's iced chocolate. Grab some milk, chocolate syrup/icecream topping, and icecream. Make chocolate milk, float a scoop of icecream in there (vanilla and chocolate work best) and drink. Straw or no.
OK, so it's not that impressive. OK, it's something that a bunch of other people can do, just given an intuitive and boring name. But think of the implications. Kids getting their daily calcium. College students getting a midnight snack (especially in summer months). Adults pretending to be kids again for a little while. Old folks getting their daily calcium.
This is pretty much my non-alcoholic drink of choice. That said, there are plenty of ways to spice up a chocolate float. Be creative. What usually goes well with milk? With chocolate?
One last note: this shit's addictive.