Usually it's my shoulder. BAM! Full force. When up in Jersey, I
  had a female friend and we'd pretend to be a married couple
  sometimes 'cause neither one of us wanted to date anybody but
  had no interest in each other either. We'd walk randomly around
  down in the evening or middle of the night, looking for a place
  to eat or find random people. She got VERY adept at throwing her
  arm out across my chest to stop me from walking across the
  street or saying, "Ken, POLE!" 'cause I'd be deep in thought in
  the times we weren't talking and... BAM. owie.