Waving your hand over the board
Like all kinds of distracting behaviour, waving your hands over the board is definitely a bad habit, especially when it is your opponent turn. But it has happened to me to play against an opponent, who purposely was waving over the board when he was making a move.
Just imagine you play against a magician. The magician who treats his every move a trick. So did my opponent. Every time he was making a move, for second or two his hand has making some kind of circles or spirals in the air. I don't know what was a purpose of playing every move like that. Maybe he tried to deceive me somehow or maybe emphasize the importance of every movement? I don't know, but it was definitely distracting.