Here is my working ball clock built out of LEGO parts. These novelty clocks were invented in the 1970s by Harley Mayenschein. You can find more information about them here: http://www.idle-tyme.com/. I had one of these growing up and, despite the colossal noise it made, I always thought it was super cool.
For those that have noticed it does not keep accurate time in the video. I just wanted to show off the mechanical components of the clock. It is currently running off of a standard LEGO 9V motor, which ends up picking up a ball every 55 seconds. In order to keep accurate time, an actual timing motor/controller would have to be used. This could be done using the LEGO mindstorms system.