We have covered plenty of fun clocks here in the past. The Chromatic: LED Color Spectrum Clock is a cool clock that uses light to display time. It has 60 LEDs and 6 different animation modes. You get Pulse, RGB, Rainbow, Traffic Light, and other modes to choose from.
You will need a CR2032 battery to get this clock working. The clock can also be powered via USB. ThinkGeek is selling these for $49.99.