We have covered a bunch of awesome clocks here in the past. Chronomeans is an awesome rolling ball clock made from rhodium- and 14k gold-plated brass, stainless steel, and anodized aluminum parts. It has 27 balls to mark the hour, every 10th minute, and each minute. Its brass drive wheel at the bottom rotates the gears. Here is how the clock works according to Hammacher:
A 14k gold-plated brass wheel conveys each ball to the topmost level of a dual-rail track, where it is deposited onto the outer rail to a single minute of time. The process repeats until a 10th ball is redirected to the inner rail where it rolls down the spiraling track to the next level to mark a 10th minute—the 6th ball at this level drops to represent an increase in the hour.
The clock comes with an acrylic cover. Not cheap though.