Chuck Howley of Dallas , Super Bowl V, it is rare but when the game is marred by incompetent play like that Super Bowl turnover after turnover, even the long touchdown pass from Unitas to Mackey was tipped twice before Mackey got his hands on it ,in cases like this I can see a losing player winning it.
Albert King won most outstanding player of the ACC tournament, he was on the losing team scoring 30+ points each game, it's pretty rare though when this happens.