A winner of a Red Dot award last year, Peter van der Jagt's Bottoms Up Doorbell is perhaps one of the best examples of repurposed objects we've come across. It's no surprise that it comes from the fertile Dutch collective that is Droog, circa 1994.
A magnet (which adds bonus points for its exposed wiring) between two different sized crystal wineglasses creates the classic ding-dong sound—but with a crystal ping—when activated. The design allows it to hang from the ceiling or on a wall. You can get it from Charles and Marie for $220 as their current featured "Soup du Jour" for the next several hours or for slightly more (but indefinitely) from Unica Home, which also sells replacement glasses.