Watch Report blog has a neat list of the world's most expensive watches. This one is Tour de I'lle by Swiss watchmaker Vacheron Constantin, which started making watches in 1755:
In 2005 this watch marked the 250th watchmaker's anniversary. Tour de l'Ile is probably the busiest watch in the world, as it has 834 separate pieces and 16 complications inside (including tourbillon, power reserve, striking-mechanism torque, moon phase, sunrise and sunset time, perpetual calendar, sky chart and many other features too impress with).
How much? $1.5 million, but you knew that If you have to ask, you can't afford it.
See the whole list: http://www.watchreport.net/index.php?page=articles&catid=8