Get a Hold of Yourself, Man!/Fan Works

Gohan actually had to punch Goku in the cheek in an attempt to get Goku to snap out of being frozen in terror after Vegeta went Super Saiyan 3 in Goku's Wish: The Return of Broly. Subverted in that it doesn't quite work.
In Dragon Age: The Crown of Thorns, the Wise Prince protagonist applies a very strong backhand to Faren, the dwarven commoner, in order to snap him out of a serious case of shut-down brain that the latter ended up in after being shoved into his worst nightmare by the Sloth Demon. He follows it with a Cooldown Hug of epic proportions. Big Brother Mentor indeed.

"There is no blood on your hands!" (and he was speaking literally)

In Relationships Series, Nanoha gets one from Vita as she becomes hysterical about the prospect of Yuuno dying on a mission, and Vita reminds her that Yuuno is determined to get back safely.
In Fail to The King, Almaz is subjected to this trope twice: Once in Chapter one to snap him out of his three-day long Heroic BSOD, and again in a later chapter to prevent another from surfacing in the middle of an invasion. Both played largely for laughs, naturally - this is a Disgaea fic after all.
In Naruto Veangance Revelaitons, Ronan does this to Sakura and his son Ekaj when they become hysterical with worry over his going off to be a Fake Defector for the Council. Considering his past behavior, it comes off as more abusive than most examples of the trope.
In The Second Try, Asuka delivers this trope almost word for word to Shinji in chapter 2, thankfully without the slapping. It is possible that had this occurred before the Third Impact, she would have slapped him, but she was probably afraid to (given what happened during instrumentality, and the fact he's the only other person left on earth).
Ace Combat: The Equestrian War: Medley hits Rainbow Dash in the face to snap her out of her Heroic BSOD.