In one episode of Black Lagoon, after a long car chase and shootout, Revy and Roberta are convinced to settle things with an old-fashioned fistfight. Robert tells her that her shoelaces are untied. Revy seems skeptical, not to mention smart, to fall for such an old trick. However, the very second she does decide to look down, Roberta delivers the first punch (or uppercut, in this case).
In the first episode of the Tenchi Muyo! OVA series, Tenchi pulls this trick on Ryoko. He's quite surprised when it works. He figures that since she's been sealed for 700 years, maybe she predates the invention of the trick. It's also probable that, since she was only pretending to try to kill him, she deliberately bought the distraction in order to prolong the chase.
And in the third movie, he does the same to both Ryoko and Ayeka. It is, again, alarmingly effective.
In one episode of Samurai Champloo, an undercover cop posing as a prostitute distracted Mugen on two separate occasions by shouting, "Look! A naked woman!" To be fair, Mugen had a swollen bruise the size of an egg on his forehead at the time, so he probably didn't have his wits about him. To be also fair, Mugen has by then a track record of being taken in by women.
She then followed up by performing a quite respectable Groin Attack, which, unfortunately for her, only turned Mugen on. (I like a woman with some fight in her).
Or perhaps not so unfortunately, given that by the end of the episode she has decided that when she finally settles down she will find Mugen and marry him.
In Ranma ½, Genma Saotome would often use this trick to cheat in games of Shogi or Go. The tables are turned on him, though, as Genma can be distracted by someone shouting "Look! A 100 yen coin!" (that's about $1). In fact, Genma has gone as far as to create a "fighting style" based entirely on pointing up, down, to the side, or behind the opponent (all of these are different techniques, even) before moving in with a surprise attack while the opponent is distracted.
In the third episode of the Strawberry Marshmallow anime, this trope is subverted when Matsuri tries this, but is not very good at it, failing miserably. Miu, the Jerkass, not fooled by Matsuri's feeble attempt, does a Look Behind You of her own back on her, which given Matsuri's vague The Ditz tendencies, is played straight, working very well. In episode 8 Miu tries it on Cool Big Sis Nobue with "Look! A UFO!", but is confused when Nobue just agrees. Then laughs at her. But then Miu launches into We Need a Distraction...
Krillin uses this move successfully on Goku in their Tenkaichi Budokai fight.
In the first Tenkaichi Budokai we see in the series, Goku falls for this yet again, By way of his opponent pretending to be holding something, and asking if Goku wanted to see what it was. When he peered in to look, the enemy smacked him.
The next true example is in the Imperfect Cell arc, right as Cell manages to sneak up behind Android 17. Tien sees him, and warns 17, who had been monologuing and believed 16 had destroyed Cell, in spite of his saying otherwise. Even though he turns around to see Cell, he's too late to react, and it costs him his life.
Played for laughs in Yo! Goku And His Friends Return. After Ava and Kado showed up, Goku and Vegeta were arguing over who would get to fight them (since they were far too weak to pose any real challenge). During the final battle, Goku pulls this trick to distract Vegeta long enough to secure the "kill", denying Vegeta the chance to throw a single punch in the special. Afterwards Vegeta complains about the dirty tactic.
During the fight for the Sacred Water, Goku tries this on Karin, his opponent. It fails, and Karin berates Goku for thinking a stupid trick would fool someone who can read minds.
Sgt. Frog opened the series with this. Natsumi tries to get her paranormal-obsessed brother Fuyuki out of bed by pointing and shouting, "Look! An alien!" Suddenly, a section of the wall where she was pointing peels away, revealing a surprised Keroro who, thinking his cover had been blown, asks "How did you know I was here?!"
Used a few times in Fushigi Yuugi, most memorably when Miaka distracts Tasuki by shouting, "Look! Nakago's doing a strip-show!"
Parodied in To Love-Ru's RPG Arc. When the "stun" spell is used...all the female characters' boobs pop out of their clothes, while the enemies (and Rito) gawk.
In Get Backers, Emishi is hiding in a maneki neko figure. He gives a fake meow, which of course doesn't faze Shido, who actually asks if Emishi really expected that to work. So Emishi points behind him and yells, "Look! It's Madoka!" Shido spins around, yelling "Where?! ♥"
In Fullmetal Alchemist, while Ed is fighting the Slicer, he mentions that Al is much stronger in a fight then he is. Halfway through the fight, he yells out for Al to attack, at which Slicer turns around to stop Al... only for it to be a hastily transmuted statue, which is all the distraction Ed needs.
Also happens in an early chapter of the manga (episode five of the first anime, not adapted for Brotherhood), when Ed confronts some of the train-jackers. He points dramatically and shouts "LOOK!" before kicking the idiot who fell for it in the jaw.
Yukari uses it in the first sports fest episode to get out of giving her class juice.
In Hajime no Ippo, this is one of Aoki's most effective techniques - he feigns surprise during the bout and slowly turns his head as if to look at something. More often than not, his opponent is so taken in by the act that they are almost forced to look away from him, leaving them totally open for a free punch.
Phantom Renegade from Medabots used this tactic after falling into the Rubber Robo hideout and found himself surrounded. After being told not to try any tricks he bows his head saying the Rubber Robos were clearly the pinnacle of evil geniuses. In the same breath he immediately pointed behind them and shouted "LOOK! IT'S THE PHANTOM RENEGADE!" successfully tricking everyone in the room.
In the Odd One Out segment of Halo Legends, Spartan-1337 does this to Pluton.
1337: Oh, hey! What the heck is that?
Brother: As if he'd ever fall for that!
(Pluton looking behind)
Sister: He did fall for it!
1337: He did? He did! Now let's get out of here!
Hanaukyō Maid Tai La Verite episode 4. While Taro is out on the town, security maid Konoe shows up with her sword. When the passersby see the sword and become afraid, Taro distracts them by yelling "What is that giant furry seal doing there!" When the passersby look where he's pointing, Taro leads Konoe away.
Kenji does it to Love Machine, a super-advanced AI, in Summer Wars to save Kazuma's avatar. He doesn't even say anything; he just points over the bot's shoulder and acts shocked. Hilariously, it works.
Usagi and Chibiusa try this on a Snow Dancer chasing them during the second Sailor Moon movie. The Snow Dancer falls for it completely, and looks genuinely puzzled when she turns around and they aren't there anymore.
Played adorably in the last episode of SuperS, where Chibi-Usa wants her private discussion with Helios while the rest of the girls watch them. She screams "LOOK! A UFO!" and every one of them turns while she gives him a huge hug and says her goodbye.
There's sort of a variation in Black Butler. There's a mass murderer on the roof of a train, along with Sebastian, and the mass murderer tricks Sebastian into not hurting him for a bit before ducking for a bridge. Sebastian, however, is totally unfazed by the rocks that hit his back and proceeds to literally throw said mass murderer off the roof, because he is, after all, one hell of a butler.
In Mai-Otome, as Shiho evaluates Arika and Erstin's cooking results, she refuses to even try the "food" they made because of how disgusting it looks. Arika tells her that there's a spiral in the sky before putting a morsel in her mouth while she's distracted. Shiho finds the food disgusting and gets angrier.
Parodied in an episode of Nichijou. There's this scene in which Nano prevents the Professor from having candy. The Professor tells Nano to turn around. Nano does so, and the Professor has the chance to take the candy, which follows an epic chase scene.
Light: Is that all the help you needed on your homework, Sayu?
Souichiro: Was your brother helping you with your homework again?
Sayu: Gee, Light! Thanks for blabbing!
A Certain Scientific Railgun: Kuroko is lecturing Saten about how she needs to stop chasing after urban legends, so Saten (truthfully) yells that Misaka is on the big screen in her gym clothes.
My Monster Secret: Asahi tries to distract Shiho by saying he saw a porn magazine on the floor somewhere. Shiho falls for it, but then returns a minute later with a porn magazine she found on the floor; Asahi is understandably shocked.
In Magical Girl Raising Project, Winterprison pins Cranberry against a wall and punches her over and over again. Suddenly, Winterprison hears her girlfriend Sister Nana scream for her to look behind her. Shocked, she turns around, but nothing is there, then Cranberry knees her in the gut and escapes. Cranberry has sound powers and is a Voice Changeling, so she was able to make Winterprison think Sister Nana was warning her about something.