It looked like the Chicago Blackhawks had won Game 2 against the Anaheim Ducks in double overtime on a stunning power play goal from Andrew Shaw, but the score was waved off at last second by the folks in Toronto. Why did that happen? According to the NHL rulebook, Shaw's headbutt of the puck into the net was a violation.
The play saw the Blackhawks fire a puck at the net, which bounced into the air, off of Shaw's head and into the goal. He clearly directed his head to butt the puck in, however, as you can see in the replays:
While that looks like a miraculous play, the ultimate example of a hockey player using his head, it's actually a violation of rule 78.5 (i) of the NHL's official rulebook. Here's an explanation of the ruling from the league, via Mark Lazarus of the Chicago Sun-Times:
And that was that. Now the Blackhawks and Ducks are heading to triple overtime in Game 2 still tied up, 2-2. Chicago fans may be upset that Shaw's goal was disallowed, but based on the current rules in place, you can't do what the Hawks forward did.