Mountain Climber
When one guy stands at attention with his dong hanging out while another guy makes the mountain climber pose.  The mountain climber then grabs the guy's dong and pulls like he's grabbing a rope to make his way up Mt. Everest.  The guy getting pulled must then yodel for the climber to stop once it becomes too painful.
Me and my buddy saw Cliffhanger the other night and decided to do the mountain climber.