In fiction, Robert Bloch provided some of my favorites...
From a short story I don't remember the title to: "She's in the other room, decorating the Christmas tree..." (as decorations...)
From Psycho when they find Mother just before she attacks.
Ramsey Campbell's "The Count of Five" had a great moment when the Merseyside Burner realizes everything he did was the result of a prank gone horribly wrong and not a curse.
From comics (and the movie though it had more impact the first time I saw it), The Watchmen: "Stop me? Do you honestly believe I would be telling you all of this if you had any chance to stop me? It all happened, five minutes ago."
From a movie - not a single moment but the final point where everyone, including the MC, must accept the truth about the whole story in "The Sixth Sense" (funny story there - at the very beginning I almost figured it out, then got sucked into the story, and did not remember that there WAS supposed to be a twist ending until about five minutes were left, and, just as the reveal hits, realized that was the only possible twist it could have).
From another movie (if you can't identify which one ... well...): "Relax, miss, I've got you." "You've got me? Who's got YOU?"
I love a good reversal of expectations, though it can be overdone. or just a comic turn of events in something otherwise not really comedic. Sure some comedies can stick with you (saw one today with two beautiful moments - "Abbott and Costello Meet Frankenstein"; the bit where they run into a room, push a bed against the door, and congratulate themselves for blocking the monster ... only to realize, as he opens it, that the door opened OUT of the room and the very last moment: Abbott: "Well, with Dracula, the Wolfman and the Frankenstein Monster all gone, there's nobody left to frighten us." Vincent Price's voice: "Oh, that's too bad. I was hoping to get in on the excitement." A&C: "What? Who?" Price again: "Permit me to introduce myself; I am the Invisible Man")
Oh, and a very obscure one, from the rule book for the roleplaying game "Chill"
"Now picture the PCs in their room for the night, kept awake by something scratching, scratching, scratching at the door. It stops for a while, they hear something heavy moving around, then it starts again. All night long.
And then the sun comes up, streaming through the windows ... to reveal the scratch marks on the INSIDE of the door."
In this scene in Okami, Amy thinks she's won but then gets destroyed by the final boss after failing at her victory howl, and all hope is lost in a world where gods aren't worshiped anymore. Then, all the people she's helped throughout the story come in to aid her by believing in her, allowing her to get her godlike powers back before you obliterate the boss.
