The pain of childbirth.. 

  A husband and wife go to the hospital to give
birth.  The doctor tells them they have a new
machine that can transfer some of the wife's
pain to the father.  The husband says, "Ok, hook
me up, I want to be as supportive as possible".

  The doctor sets the machine at 10% and  
labor progresses.  The husband is feeling all 
right so he tells the doctor to turn the machine 
up to 20%.  This is still very tolerable so he 
tells the doctor to try 50%.  He is still feeling
great so he tells the doctor to turn it all the 
way to 100%.  
  The wife is having no pain at all and delivers 
a beautiful baby.  The husband gets up and is in  
good shape and because the wife has gone through 
very little pain they are ready to go home.

  When they pull into the driveway they find the  
mailman on the porch dead.