I can't think of a specific moment in a game that I would have been upset had it been spoiled for me. I can think of plenty of TV moments that I would have been really upset about, but for games, the moments that mostly blow me away aren't really story twists and turns, but gameplay experiences that can't really be spoiled.
Liie, Winter in The Last of Us. I don't think you can spoil that for me because what made it great was the gameplay of that section, not necessarily the story. Maybe already knowing the story would remove some tension from that gameplay, but it's still worth experiencing for yourself.
Actually, now that I think of it, if the sunset sand surfing in Journey had been spoiled for me, it wouldn't have had nearly the impact that it did.