Throwing stones onto the goban
Once I was playing a 9 stone handicap game with someone in a particular uni club.
After I placed my handi stones on the board and asked my opponent to begin,he started by tossing his first white stone onto the board.
My attention was elsewhere at that point so I wasn't sure if this had just happened. So I responded to this move seriously.
He continued to toss his next stone onto the board. When I realised what had happened, I was so shocked I couldn't move.
After about thirty seconds of staring at the stone, I closed the stone box, bowed and left the table.
I was unable to play a game with someone who shows no respect to his opponent, himself, or go.
-- Anonymous
WillerZ Perhaps he was trying a Random Opening?; it can lead to interesting games.