when I was 13 I visited the scientorium(sp?) in san francisco and they had this cool display with cold and warm water running through two seperate pipes. The pipes were sufficiently thin and close so that gripping them would put the nerves in stimulus by both heat and cold. This confused the nerves and produced an extremely painful feeling but absolutely no tissue damage.
Now, thai kick boxers get rid of the nerves in their legs by bashing things. Not that I want to, but could I use the hot/cold water pipe apparatus to kill sensory nerves by overloading them?