"Powers o' Darkness!" Jack exclaimed, focusing his one eye that hadn't swollen shut on a point in the middle distance. "I do believe that elephant is fookin' that camel up the arse—or is it t'other way round?"
The usual subversion in The Silver Pigs by Lindsey Davies—notable for the villain mocking Falco for using "that old trick" in Ancient Rome.
In The Lies of Locke Lamora, Locke is getting his ass kicked by the Grey King, and tricks him into thinking that Jean (who is a much better fighter than Locke) is right behind him. While he's distracted, Locke steals the dagger from his enemy's belt and stabs him to death.
In the Time Warp Trio book Your Mother Was A Neanderthal, the eponymous group pulls this on a group of cavewomen using the phrase "Woolly mammoth!" The boys are aware that the targets don't understand English, leaving the strength of the ploy in the body language and emotional acting.
Fablehaven has a bizarre version of the not-looking version. Kendra is trapped in a cave by the human form of Navarog (both the literal and figurative dragon for theBig Bad), and Raxtus appears behind Navarog; Kendra makes an expression of genuine surprise. Navarog comments that she's over acting, lectures her on the lack of ingenuity, and says she needs to try harder on this trope to fool him, even saying "If something tried to creep up on me, I would know". This comes back to bite him, literally, as Raxtus eats him.
Sherlock Holmes actually does this in one famous scene, though being Sherlock Holmes, he does of course give the trope a little finesse. (All protestations to the contrary notwithstanding, he has to be having a bit of fun at Watson's expense. It's not like he didn't have Mrs. Hudson as a gauge, if nothing else.)
"What do you hear?" he demanded. "Watch that doorway," she replied, pointing. He wheeled, sword ready. Only the empty arch of the entrance met his gaze. Then behind him sounded a quick faint scuffling noise, a half-choked gasp. He whirled. Thalis and Natala had vanished.
In The Bartimaeus Trilogy, Bartimaeus once defeated a large number of Utukku spirits at the battle of Al-Arish by repeatedly using this trick. He explains that the only reason it worked is because Utukku are invariably Too Dumb to Live. When one of the survivors encounters him trapped and helpless a thousand years later, he attempts to kill Bartimaeus with a spear, having grown smart enough in the meantime not to fall for the trick when Bartimaeus tries it again... so of course, on this one occasion there happen to be a pair of powerful, extremely unfriendly Djinn sneaking up on the Utukku whom he fails to notice, leading to his death.
Additionally, in Ptolemy's Gate, when Nathaniel is facing off agains the mercenary for the final time, he tells him that his doom approaches from behind and shouts for "Belazael" to attack. There is no Belazael, but he tactic does get the mercenary to look behind him, allowing Nathaniel a few seconds to make his move.
In the Alternate History novel West of Eden by Harry Harrison, Vainte uses the ability of humans to lie by instructing her captive human Kerrick to shout "Look, a ustouzou (human) in the trees!" on a particular signal. She later stabs a rival with a human arrow and gives the signal—fortunately the startled Kerrick remembers his cue.
Chas McGill pulls this on Boddser Brown when Brown has him cornered. Turns out that Clogger has just arrived behind Boddser to lay the smackdown on him.
In The Lost Hero, Piper plays this straight up in an admittedly obvious trick, but it works because as a child of Aphrodite she has the ability to charmspeak which causes not only her target to look, but everyone else as well.
Isaac Asimov's Lucky Starr and the Big Sun of Mercury: Bigman Jones is holding Jonathan Urteil at blaster-point in the Mercury mines when Urteil looks over Bigman's shoulder and says that Lucky Starr is coming back. Bigman looks, and Urteil quickly gains the upper hand.
Never in his life had Bigman so hated himself. To be tricked and hoodwinked this way. He almost deserved death. He would almost rather die than ever have to face Lucky and say, "He looked behind me and said you were coming so I turned..."
Pat McManus reminisces about this trick's prevalence in the Westerns of his childhood in "Meanwhile Back at the B-Western."
In The Stainless Steel Rat by Harry Harrison, Angelina holds a gun on Jim, and his eyes widen as he looks over her shoulder. She scoffs at him for trying to pull that trick, and is then disarmed by the man coming up behind her.
This works in another Harry Harrison novel The Ethical Engineer because the protagonist is on a Death World, so when someone tells you to look behind you in an alarmed voice, you take them seriously.
Star Wars: Kenobi: After foiling his False Flag Operation and pursuing him over the desert, Ben shouts to Orrin to watch out for actual Sand People behind him, but he refuses to believe it and runs into their ambush.
In the German crime parody Gestatten, mein Name ist Cox! we have it played straight AND subverted at the same time. Cox distracts a baddie by turning his attention to a car that allegedly had been following them for miles. The baddie falls for it and is overwhelmed. Subversion: the cavalry WAS in the car following them all along.
Requiem for an Assassin (aka The Killer Ascendant) by Barry Eisler. John Rain is being held at gunpoint by the Big Bad, who demands to know where his friend Dox is (not knowing that Dox was too severely injured to accompany Rain). Rain replies, "Dox, take him out!" and jumps the Big Bad when he tries to move out of Dox's assumed line-of-fire.
In Winner Take All, Rain walks right up to a Badass in a Nice Suit who's been sent to kill him and says, "Is that birdshit on your shoulder?", then attacks him when he turns to look. He notes that you shouldn't wear an expensive suit in their profession because you're always going to be worried about damage to it.
The Trials of Apollo features a use of this trope by Apollo in The Dark Prophecy that works especially well, since the ones he tricks are very gullible and slow to turn around. Apollo then goes further to thoroughly lampshade how this trope is apparently Older Than Dirt, stating that it was first recorded on Mesopotamian clay tablets.
Fate/strange fake: When Sigma is attacked by False Assassin, Sigma looks over her shoulder and yells, "Now! Stab her, Chaplin!" When she turns around to counter this nonexistent threat, he throws a flashbang grenade at her and runs.