Plot hole: When the game goes into Sudden Death, the teams are seen taking a brief timeout at the benches. The only problem here is: during the Stanley Cup playoffs, whenever a game heads into OT, the ice has to be resurfaced and both teams are sent to the dressing room. If this had happened, the Penguins would certainly have noticed that their dressing room was bullet-riddled from the fight that occurred earlier and would have - at the very least - figured something was up.
Plot hole: Luc Robitaille scores the game-tying goal with no time left on the clock, 0:00.00, sending the game into 'sudden death' overtime, hence the title of the film. The only problem is you cannot score a goal in an NHL game with no time left on the clock. It's impossible. Even if there were .5 seconds left, both teams would have to have an ensuing faceoff for the rest of the time to expire.
Plot hole: It's hard to believe that not one single civilian at the game (other than the main characters) is aware of what is going on outside. With hundreds of cops and paramedics surrounding the building and the explosions that happen during the game someone would have figured out something was up long before the end of the film.
Plot hole: Assuming for the moment that the terrorists got the money they wanted...then what? With the building surrounded they wouldn't have been able to escape without being seen by the authorities, the vice president and everyone else know what the main bad guy looks like, and the helicopter they had couldn't carry them all. So how would they get away with it?
Plot hole: Darren knew that the terrorists would kill everyone with the bombs if they didn't get the money they wanted, problem is he was never told when the bombs would go off so when the third period expires with the sudden death goal, he had no reason to suspect that's when the bombs would go off.