that freaking goal by Steve Smith into the Oilers' own net against Calgary in 1986. If the Oilers hadn't managed to eliminate themselves, they would have gone to 7 finals in 8 years and won at least 5, and probably 6 of them. (Yes, I know it's hyperbole to argue that the one goal by Smith cost them a series they lost in 7 games).
And Edmonton won another cup in 1994 in New York.