In a memorable McDonald's commercial from the 90s, a boxer is being badly beaten until his father/coach reminds him of how one of his childhood birthday parties at McDonald's was ruined when someone stole his fries. Dad points to the boxer's opponent and says "It was him". During the display of the McDonald's slogan the boxer One-Hit KOs his opponent. Link for the curious.
Anime and Manga
In Samurai Champloo Mugen and a highly attractive ninja girl are in a room surrounded by more than 20 highly trained ninjas that want to kill them both for stumbling onto a counterfeiting operation. The girl, who has already used sex to motivate Mugen before, promises to do something too perverted to be spoken aloud if Mugen helps her. Mugen curb stomps the armed ninjas barehanded.
Right at the beginning of Love Hina, Keitaro tells Shinobu that she'd be able to get into Tokyo University because he got accepted. Almost immediately, he realized in his head that he just helped further the misunderstanding everyone had at the time of thinking he goes to Tokyo University.
In Attack on Titan, after a soldier attempts and fails to reclaim his friend's body (which subsequently forces the dumping of other recovered bodies), Levi gives him a Survey Corps badge which he claims belonged to his friend. It's implied that the badge actually belonged to Petra, one of Levi's own fallen squad members, as he was previously shown taking the badge from her uniform.
In the End of Evangelion, (26-year-old) Misato offers (14-year-old) Shinji this pearl after giving him a passionate kiss: "We'll do the rest when you get back." (Well, she doesn't.) She then shoves him into an elevator, smiles as it closes, and immediately slumps to the floor as she bleeds to death. The kiss is a sexual stimulator for him, as Shinji's lack of sexual confidence is what chains him to inaction for at least the first third of the film. Unfortunately, her shoving him into the elevator is the only tangible difference she makes for him plot-wise as her lie tells on itself when Shinji tastes/sees her blood inside his mouth/on his hand.
Considering the potential and ambiguous nature of the Rebuild series, it may have been an unintentional truth! Depending on the content of the fourth and final movie . . . .
In the Over the Edge event, Frank Castle was brainwashed into believing that the death of his family was set up by Nick Fury of S.H.I.E.L.D., so that Castle would focus his unquenchable wrath on killing Fury.
In The Punisher MAX, he is tricked into believing a young woman has been kidnapped by a prostitution ring (in fact, one drug dealing gang tried to get rid of a rival gang by siccing him on them). Naturally, both gangs end up slaughtered by the end.
In the fifth Scott Pilgrim book, Scott goes to fight the twins and rescue his friend Kim who is being held hostage, but struggles because he's demoralized due to the serious argument he just had with his girlfriend Ramona and the fact that their relationship seems to be on the edge of a breakup. As the twins mock him about this, Kim's phone beeps because the battery is dying, but Kim tells Scott that it was Ramona calling, and that she's cheering him on and waiting for him to get back so they can patch things up. Scott immediately kicks the crap out of the twins.
In The Avengers, after Coulson dies at Loki's hands, Fury tosses a small pile of bloodstained vintage Captain America trading cards (Mint Condition!) at Cap, as part of his attempt to use it to galvanize the Avengers. The cards were not on Coulson's person at the time, but in his locker. WMG theories abound that Coulson's death itself was a motivational lie, eventually proved when he appears alive and well in the Agents of S.H.I.E.L.D. TV series and then subverted. Coulson was really dead, but Death Is Cheap.
In The Blues Brothers, while Jake is in prison, Elwood lies about keeping in touch with the rest of the band so that Jake doesn't lose hope.
Elwood: What was I gonna do? Take away your only hope? Take away the very thing that kept you going in there? I took the liberty of bullshitting you. Jake: You lied to me. Elwood: Wasn't lies, it was just... bullshit.
While he's mostly just trying to save his own skin, Spicoli in Fast Times at Ridgemont High makes it look like a rival high school wrecked Charles Jefferson's car, instead of Spicoli himself. Jefferson winds up taking that school's team apart in the next football game.
In Die Hard with a Vengeance, John McClane only gets Zeus Carver to help him investigate a spate of bombings by telling him that one bomb was discovered in a black neighborhood. Towards the end of the movie he admits that it wasn't anyplace close to where he'd claimed it was found.
During one scene in A Knight's Tale, Roland tells William (who is a peasant pretending to be a knight) that his jousting opponent is cruel to his peasants. After William angrily charges off to thrash the opponent, Roland remarks that it's probably true.
The Oracle from The Matrix does a long term version of this to Neo, and it's hinted that she does this regularly to help people unlock their potential and think differently. In fact, that's exactly her motivation — although it takes six Ones to make one of them see outside of the Matrix (and the Architect's version of the prophecy) to make Neo take the needed third option to fix things.
The famous Star Wars scene where Obi-Wan Kenobi tells Luke that Vader killed Luke's father, then later justifies it as Metaphorically True can easily be seen as this. In Episode 3 it is shown that this was also likely Obi-Wan's belief at that point, this was what allowed him to nearly kill Vader at Mustafar.
The Dark Knight does this to the city of Gotham and Batman himself during the ending. In order to prevent mass chaos from the fallout of Harvey Dent's actions as Two Face, Batman willingly framed himself for the murders Dent committed, so that Harvey Dent could remain an inspirational figure to the rest of Gotham. Alfred also burned Rachel's letter saying she would marry Harvey, to spare Bruce further pain from her death.
The trope is further examined and ultimately subverted in The Dark Knight Rises. Dent's "murder" by Batman was used to rally support for the passage of the Dent Act, which curtailed civil liberties but also led to the near-elimination of organized crime in Gotham. However, Gordon's wife left him for covering up Harvey Dent's actions. Bruce retires from being Batman and becomes a recluse out of grief over losing Rachel, due to being convinced she would have married him if she's lived. And when Bane reveals the lie about Dent, the downtrodden citizens and prisoners join Bane's army as retribution. Bane's "revolution" also serves as a Motivational Lie, since it was only intended as a distraction before blowing up Gotham.
The Dark Tower series has an example of this being used as a training method. Roland just can't get Susannah to focus on her gunslinger training until he resorts to reminding her of the traumas she suffered at the hands of racists before and during the black Civil Rights Movement. He goes so in depth that she practically gets lost in the memories. Then he suddenly points at the targets and shouts "There they are, shoot them!" Susannah does, but when she calms down she calls Roland out for manipulating her that way.
Brisingr from Inheritance Cycle had Elva lie to Nasuada before the Trial of the Long Knives, in order for her to win the trial. She told Nasuada that she would win, and that gave her the confidence to endure longer, but if she had let things be, Nasuada would have lost.
In Interesting Times, Rincewind gets out of a pursuit by running into a room of sumo wrestlers, yelling that one of his pursuers has a sandwich on him, and ducking out of the carnage.
Live Action TV
At the end of the Battlestar Galactica (Reimagined) pilot, Adama tells the fleet of a legendary thirteenth colony called "Earth", that he knew actually existed, and that they could flee there. President Roslin quickly calls him out on it in private. Later on they do discover that Earth is real, and start trying to find it.
Laura Roslin: There's no Earth. You made it all up. President Adar and I once talked about the legends surrounding Earth. He knew nothing about a secret location regarding Earth, and if the President knew nothing about it, what are the chances that you do? Adama: You're right. There's no Earth. It's all a legend. Laura Roslin: Then why? Adama: Because it's not enough to just live. You have to have something to live for. Let it be Earth. Laura Roslin: They'll never forgive you. Adama: Maybe. But in the meantime I've given all of us a fighting chance to survive. And isn't that what you said was the most important thing, the survival of the human race?
In the Season 4 finale of Breaking BadWalt convinces Jesse that Gus tried to poison a child with Ricin. Really, Walt poisoned the kid and told Jesse about it in order to get Jesse on his side.
On the American edition of Kitchen Nightmares, Gordon Ramsay calls Moe, one of the brother co-owners of the "Oceana" restaurant, "a busy idiot", being involved in all the wrong areas. Moe was about to pick a fight with Ramsay until Rami, his more level-headed co-owner brother, defused the situation by telling Moe that "busy idiot" is actually a compliment in British English.
Done in Star Trek: Deep Space Nine during the Dominion War arc, when Sisko and Garak form a plan to trick the Romulans, (who are neutral in the war) into thinking that the Dominion/Cardassian alliance is about to betray and attack them instead of settling for the "I'll kill you last" version of You Will Be Spared.
On The Wire, StringerBell used the classic villain version to set Brother Mouzone (a Professional Killer hired by Stringer's partner and that was getting in the way of Stringer's plans) and Omar (a badass who robs drug dealers and has a personal vendetta against Stringer) against each other. Whoever dies, Stringer wins. They both live and team up for revenge.
After Stringer's death, the soldiers of the Barksdale Organization assume that their rival Marlo was responsible. Even after Slim Charles (the head of Barksdale's muscle) finds out that Marlo had nothing to do with it, he encourages the lie, because it'll make the troops do anything to win.
Buffy the Vampire Slayer: in early Season 3 episode "Faith, Hope and Trick", Giles needs to know the exact circumstances of Angel's death for a spell to prevent the return of Acathla. Buffy finally summons the courage to tell him that Angel's soul returned, just before Buffy was forced to kill him. Once Buffy leaves, Giles reveals to Willow that there was no spell; it was a ruse, to get Buffy to open up to them and to accept what she'd done.
A more controversial example is Xander's lie to Buffy so she won't hold back when fighting Angelus. Willow had told him she may have a chance of restoring his soul, so Buffy would need to stall Angelus (who is about to bring about the end of the world). Xander relays this as, "Willow said kick his ass."
In the Doctor Who episode "The Big Bang," when Rory is having a Heroic BSOD over killing Amy while hypnotically controlled and doesn't believe he's human, the Doctor tells him one to show him otherwise:
The Doctor (sneeringly): Trillions of people have just been wiped from existence! Your girlfriend isn't more important than the entire universe. (Rory turns the Doctor to face him and slugs him in the jaw so hard he falls flat on his ass) Rory: SHE IS TO ME!! The Doctor (delighted): Welcome BACK, Rory Williams!
In the Supernatural episode "All Hell Breaks Loose, Part One" (S02, Ep21), Sam tries to get the others ready to fight the demon by pretending things will be all right if they work together, but he has his own doubts. Jake realizes this, and says, "It doesn't matter if we believe it. Only matters that they do."
In Mass Effect 3, after the fall of Thessia and the revelation that the Prothean beacon was the main reason why the Asari are technically superior to the rest of the galaxy, Liara confronts Javik and demands to know why he didn't fix things, because as a Prothean he's supposed to have all the answers. Depending on what you do, he'll tell her that his people believed that the Asari were the best hope for this cycle, which calms her down. After walking out of the room, Shepard can ask whether or not Javik was telling the truth. Javik doesn't give a straight answer, but it's implied he's just telling her what she wants to hear.
When Mario becomes sick in Mario & Luigi: Superstar Saga Luigi is told to go to a cave where a horrible man-eating monster lives to procure a plant that will help Mario recover. The player is forced, due to Luigi being too terrified to even jump, to visit a resident magician who hypnotises Luigi into thinking he's Mario. When Luigi snaps out of it he already has the plant, so it's a slight aversion in that he never seems to realise that he's just as good as Mario when he's not terrified.
In Ghost Trick, Ray will tell Sissel that as a ghost, he'll cease to exist at dawn. This only serves as a motivation to get Sissel to the right place at the right time to resolve the game's main plot.
In The Last Days of Foxhound, the spirit of Big Boss claims to have been responsible for telling Liquid that he was the inferior clone to Solid Snake and filling Liquid's head with completely erroneous ideas about genetics so that Liquid would be motivated to excel rather than just relying on natural ability.
In strip #22, Roy needs Belkar (the party ranger) to track down a chimaera. Since Belkar has no idea he can do that, Roy tells him that the chimaera made fun of how short he is. Belkar gets angry and starts tracking it.
Later he uses a similar trick on both Belkar and Haley. He wanted them to join him in his sidequest, which they refused, so he made up that there were giants which are worth a lot of XP to make Belkar come with him. He told Haley that they are king giants because she cares more for gold than XP.
In the first case, Gohan has been transformed into a giant ape and is destroying everything in sight as a result. Goku gets him to concentrate on Vegeta by saying that Vegeta was responsible for killing Gohan's pet dragon. As Vegeta wasn't even on the planet when it happened, he gets rather pissed by this.
In the parody of the Lord Slug movie, Goku is knocked out and awakens to find the planet frozen. Because he's Goku, he assumes that because it's snowing it's Christmas, and that the Villains of the movie are looking to wreck Christmas like a different group of bad guys Goku had fought before. When Goku is losing the fight to Lord Slug, King Kai reminds Goku that he's fighting to keep Christmas from being wiped out, which sends Goku straight into Unstoppable Rage.
During Bennett The Sage's review of the anime version of Demon City Shinjuku, Sage mentions that one of the characters is named Mephisto, then cringes as that summons Linkara who begins ranting about that one Spider Man arc that everyone hates, because it also featured a character named Mephisto. To get rid of Linkara, Sage claims that another reviewer was badmouthing some of Linkara's favorite comic writers. Linkara promptly storms off for revenge.
Sage: Hey, did you hear that The Last Angry Geek called Alan Moore overrated? Linkara: Well... I can see that. The man can only write so many classics before he taps out. Sage: Wait, did I say Alan Moore? I meant Neil Gaiman. Yeah, Neil Gaiman. Linkara: WHAT?!! Where is that slimeball, I'm going to rip him to shreds!
In Worm, Tattletale lies to Taylor about Grue's death so that she wouldn't blame herself for his death at a crucial time.
In the "My Three Suns" episode of Futurama, Fry accidentally drinks a planetary Emperor with a liquid body, which results in a You Kill It, You Bought It situation. That is, until it gets revealed that the Emperor is still alive in Fry's body and the Emperor's subjects start trying to get the Emperor out. Violently. As an alternative to letting the watery beings kill Fry, the gang tells Fry that Leela is dead to get him to cry the Emperor out instead.
David Xanatos from Gargoyles used several such lies to trick Derek Maza into holding a grudge against Goliath and remaining loyal to Xanatos.
Osmosis Jones had Jones telling Drix about some sugar pills he knew that cured cancer in an effort to motivate him. This exchange happens a bit later:
Drix: "Did you really know some sugar pills that cured cancer?"
Jones: "Pbbbt! Heck no! But it makes for good pep talk, don't it?"
Similar to the above, on The Simpsons Dr. Hibbert tells Bart & Marge that the only way to get some superglue off his face is with several painful injections into his spine. This makes Bart sweat with nervousness, which makes the glue come off.
Marge: What happened? You didn't do anything! Dr. Hibbert: Oh, didn't I? [laughs] Nothing dissolves glue better than human sweat. I knew Bart would panic and start perspiring at the sight of this button applicator! Bart: Couldn't you have just turned the heat up a little? Dr. Hibbert:[sinister] Oh, heavens no! It had to be terror sweat!
Played with in the South Park Season 1 episode "Damien", in which Jesus is losing to a boxing match against Satan. Stan encourages Jesus with an inspirational quote, claiming that it was something Jesus said. After Jesus gets back into the fight, it's revealed that the quote is actually from Star Trek; however, Stan wasn't intentionally lying, he'd just gotten the source of the quote mixed up.