Automaton of Leonardo's Mechanical Hammer

Here's a nice looking model from the folks at PaperPino. This is a paper model made up of 44 parts that can be assembled without glue. A system of removable interlocking pins holds the model together.

From the PaperPino Site:
This is one of the simplest machines designed by Leonardo in order to improve the human performance. A lever connected to the hammer is moved by means of an eccentric cam. At each turn of the handle, the hammer gives a stroke. As a matter of fact, the real hammer is supposed to be powered by a water paddle-wheel. An implementation with a paddle-wheel powered by sand is planned for the next future.

Check out Leonardo's Mechanical Hammer paper model.