The Ssahng Jeol Bong (better known as the nunchaku or nunchucku) is a weapon which benefits coordination and dexterity as well as upper body conditioning. 

The history of the Ssahng Jeol Bong is quite interesting.  "In its earliest form, the Ssahng Jeol Bong served the farmer in the harvesting of his crops by separating grain from the shaft.  Picture a harvest of grain laying on a specially prepared surface.  The farmer would beat the crop with a tool that was comprised of a long staff with a shorter stick attached to the end by a rope.  The length of the longer staff would help generate power into the strike, making the job somewhat easier for the farmer.  By beating the crop with the tool, the shorter stick would make the grain separate from the plant so that it could be harvested.

"During times of war, this farm tool could easily be used as a weapon.  Often called a Chul Te or Dur Ree Ge, we may be able to picture it easier if we think of a mace.  In these battles, the length of the longer staff allowed the warrior to stay at a safer distance from his opponent and would also aid in the generation of power into the strike.  As peace time prevailed, the warriors, with little to do but train, refashioned the Chul Te into smaller versions until we have the design we are familiar with today."  Introduction to the Ssahng Jeol Bong, 'Ssahng Jeol Bong Manual', Copyright Protech Training Systems, 1996