Check out this great wood automaton by Tony Anagnostopoulos. The piece took him two years to make, but it was worth the effort! He documents the process thoroughly on his blog.
Timing is critical to this piece. The slow movement of the turtle and the finger build up a lot of anticipation. The automaton's cycle is extended with the use of a worm and screw mechanism. A close up of one of one he made is shown below.
The fast reaction when the finger taps the turtle's shell is just what the piece needed for a finish to the cycle.
Here is a link to the Amateur Automata Maker blog.