One of these nights, maybe before the end of this regular season, probably in a game when the second point will not be so vital, a goaltender is going to run an opponent. The shootout participant will be someone like Jason Blake or Mason Raymond or Mikhail Grabovski, one of the growing number of forwards to score over the last year utilizing the Spin-o-Rama. He'll skate toward the goal and prepare to stop on a dime a few inches inside the crease. Just as Blake and Raymond and Grabovski, Todd Bertuzzi, Pierre-Marc Bouchard and others have done, the shooter will have his head down momentarily as he stops and prepares to spin. (Watch the videos: few have pulled off the move with their head up all the way). In some NHL rink, a goaltender is going to take one bold step for the rest of his fraternity. In a pre-meditated, but non-violent fashion, the goalie is going to send one of the Spin-o-Rama boys on his rear end.
It may cost his team a point in the standings. It may cost the goaltender some money, but it will have been worth it.
I will go a little further. I don't think it's against the rules. In fact, I'm sure (unless there's some corner of the rule book I don't know about) it's allowed. If the goalie is not making illegal contact (e.g. check to the head, cross-checking, elbowing), I don't see any reason why the goalie can't knock down the guy with the puck if the guy decides to stop with his head down two feet in front of him.
And, even better, even if the goalie does check the guy illegally -- say, by cross-checking him -- it's not even a penalty. Check it out:
NHL Rule Book 25.4 - Violations During the [penalty] Shot
When an infraction worthy of a minor penalty is committed by the goalkeeper during the penalty shot that causes the shot to fail, no penalty is to be assessed but the Referee shall permit the shot to be taken over again. Should a goalkeeper commit a second violation during the penalty shot and the shot fails, he shall be assessed a misconduct penalty and the Referee shall permit the penalty shot to be taken over again. A third such violation shall result in the goalkeeper being assessed a game misconduct penalty. When a major or match penalty is committed by the goalkeeper that causes the shot to fail, the Referee shall permit the shot to be taken over again and the appropriate penalties shall be assessed to the goalkeeper.
The goalkeeper may attempt to stop the shot in any manner except by throwing his stick or any object, or by deliberately dislodging the goal, in which case a goal shall be awarded.
To sum up: goalie can do anything except throw his stick or knock the net off. And any otherwise illegal contact, which would normally result in a penalty, is at worst a do-over. (though, I guess by the third offense of the second goalie -- at which point they both would have been tossed -- you would run out of goalies.)