I dealt to a guy who is always slow roling and had this situation:

Two players at showdown, the other player shows his hand and this guy picks up his cards and looks at them one at a time shuffling them in front of his eyes. I say "Show them or Muck Them sir" He says "time". I said "You can't have Time". He says "why not?" I say "The game is over show them or muck them." he stares at me like I'm speaking a foreign language. "FLOOR !!!!!" Just as the floor gets to the table he turns over the nuts. I tell the floor what just happened and the Player says "Why can't I do that? Its the best part of Poker."

I swear if I was a player in that game I would have punched him.