In The Lady Killers remake, the Vietcong slaps the Jock to bring him to his senses, because the latter was freaking out over one of their party members losing a finger and bleeding all over the place.
Spoofed in Airplane!, when virtually everyone on the plane lines up for a chance to slap a hysterical woman, with increasingly violent means.
In the sequel, she testifies about it in court. After the flashback, she goes into hysterics from the memory. Guess what happens?
Played somewhat straight in Clue, when Mr. Green uses it to calm a hysterical Mrs. Peacock.
Mr. Green: Well, I had to stop her screaming...
Inverted during Wadsworth's final recap of the film, when he re-enacts it by slapping an otherwise calm Mr. Green. The slap actually drives Green to hysterics. It does, however, lead to one of Tim Curry's many great line deliveries in the film.
Wadsworth: Well, I had to stop her screaming...
Subverted to great effect in The Producers, where a glass of water to the face just adds "I'm wet!" to the list of complaints, and slapping them makes it worse still: "I'm in pain! I'm in pain and I'm wet and I'm still hysterical!"
The iconic scene from Moonstruck is Cher slapping Nicolas Cage and yelling at him to "Snap out of it!" when he says he loves her.
Undercover Brother. When Lance panics over the impending detonation of a Self-Destruct Mechanism ("We're gonna die! We're all gonna die!"), the title character repeatedly slaps him to bring him to his senses.
In Maverick, the title character comes unglued because he thinks all of his money has been stolen. His friend Chief Joseph slaps him and says "Pull yourself together! Everyone's looking!"
Parodied in Monsters Unleashed when Scooby and Shaggy are under attack by monsters. After Shaggy hysterically yells at Scooby, Scooby slaps him ("I needed that") twice ("I needed that too"), then punches him in the face ("You're pushing your luck, Scoob!").
Patton's preferred method of dealing with hysterical soldiers.
The Thing from Another World. A soldier is is hysterical after seeing the eponymous "Thing", and is brought back to reality with a cold glass of water to the face.
Used as a Running Gag in the indie film To Die Is Hard, where one character slaps another -- often saying the trope name verbatim. Even if the person that was slapped was calm in the first place.
The film adaptation of Scott Pilgrim Vs. The World, as Steven Stills begins freaking out about the crowd their band is about to play for, Scott realizes that the two girls he's balancing at the moment are beginning to converse. At this point, he slaps Steven, telling him: "We need to play now, and loud."
Disney's Aladdin. Iago to Jafar. Jafar was laughing uncontrollably because he had just realized that Prince Ali was Aladdin. No "I needed that", though -- Jafar is distinctlyungrateful for the intervention.
Then again, it doesn't take much to get Jafar to laugh uncontrollably.
Iago: Oh, boy. He's cracked. He's gone nuts. Jafar, Jafar! Get a grip! (grabbed around the throat) Glah! (wheezing)Good grip.
Extra points for the hilarious clang clang clang sound when Iago knocks on Jafar's absurd headdress to bring him back to his senses.
Neatly done in Toy Story, when Buzz is angsting hysterically about his recent realization that he is just a toy; Woody picks up Buzz's own arm (which had previously become detached), opens Buzz's helmet dome, slaps him with it, and then closes his dome. Buzz calms down, admits he has a problem and that he can deal with it... and immediately begins howling again.
In Cube 2: Hypercube, Kate does this to Jerry when he starts to ramble too much.
Edna: You are Elastigirl! My god! Pull yourself together! What will you do, is this a question? You will show him you remember he is Mr. Incredible, and you will remind him who you are! So, you know where he is. Go, confront the problem, fight, win! And call me when you get back, darling, I enjoy our visits.
Disney's The Great Mouse Detective has Basil and his sidekick Dawson in the Death Trap, Basil doing nothing but bemoaning how Ratigan's outwitted him until Dawson snaps and gives him an angry verbal slap back to reality.
Dawson: I know you can save us, but if you've given up, then why don't we just set it off now and be done with it?
Basil: Hehe, set it off now. (epiphany expression) Set it off now? Haha, ha, yes! We'll set the trap off now!
Jim: Yeah, Flint's trove? You know, loot of a thousand worlds?
B.E.N.:(breaking up at places) It's-well, it's... it's all a little-little-fuzzy. Wait! I-I re-re-remember! I do. I-Treasure! Lots of treasure! Buried in the centroid-centroid-centroid of the mechanism! And there was this big... door... opening and closing and opening and closing... And captain Flint wanted to make sure nobody could ever get to his treasure... so I helped him... (sputtering) Naaah! Data inaccessible! (loses it) Reboot! Reboot! Reboot!
Jim: B.E.N.? B.E.N.! (slaps him)
B.E.N.: And you are...?
Jim: Wait, wait, wait! What about the treasure?
B.E.N.: I wanna say Larry.
Used in Night of the Living Dead. As Ben is trying to fortify the house that the main characters are trapped in, Barbara is trying to get Ben to help her go out and find her brother Johnny so he can join them in the house, safe from the zombies. Meanwhile, Ben is trying to persuade Barbara to give up Johnny for dead. Eventually, Barbara screams at Ben and slaps him. Ben slaps her back to get her to snap out of it and also in retaliation.
Played uncomfortably straight in The Apartment, with the protagonist even looking uncomfortable witnessing a woman get slapped into consciousness.
To be clear: It was a doctor slapping a woman who had just taken half a bottle of sleeping pills.
Handily subverted in film noir Angel Face. The hero slaps the Femme Fatale to bring her out of a fit of (probably-feigned) hysterics; she stares at him indignantly and slaps him right back.
Ichi the Killer features a straight example of this. The title character has retracted into a blanket shell and is slapped in order that he faces reality.