Originally Posted by Mediocre Nachos
Technically, it's not an 8 seed over a 1 seed thanks to how they've changed the playoffs. There are no 8 seeds in the traditional sense. The top three from each division make it, then two wild cards. #2 & #3 from each division play each other, and then the worst wild card plays the best division winner, and the other wild card plays the other. It just so happens, that Chicago was the best team in the conference, and Nashville the worst wild card, so it's basically that.
Anyway, the answer is 2012. Los Angeles beat Vancouver in the first round, back when they still had true 1-8 seedings. LA actually beat the #1, #2, and #3 teams en route to the Stanley Cup and then played their toughest series there, winning 4-2. They lost a grand total of two games in the Western Conference that year.
Coincidentally, Nashville upset a division winner as a wild card last year, albeit the second best division winner.