Regular season: I'm going to go off the board a little & say last year vs. the Red Wings.
Richards coast-to-coast to tie it, followed by the OT winner by Callahan. Beating Detroit holds extra weight to me no matter how good they are.
Postseason: Game 5 vs. WAS last year, of course.
Honorable mention: Game 1 of that series a.k.a. the Chris Kreider show.
We don't know how Kreider's NHL will turn out right now. But I don't think I ever heard a rookie get a bigger cheer for their first goal at MSG than Kreider in that game. The love that was showered on him for breaking the tie early in the 3rd, followed by the roar upon hearing his name after his primary assist on Richards' goal shortly thereafter was incredible. I couldn't stop rewinding the DVR to see those plays after the game ended. I'm a man but I literally shed a small tear of pure joy for the youngster.