The Doctor: Pass me the vibro-cutters.
Clara: They're in my pocket.
The Doctor: Come on then, pass them to me.
Clara: In my other jacket. At home.
The Doctor: Why have you got two jackets? Is one of them faulty?
A character rushes out of the room and a closeup shot reveals they've left their firearm behind, or some other crucial item like a mobile phone or the Amulet of Dependency. Naturally they're going to need that item for the very situation they're about to head into. Bonus points for an Oh, Crap!.
- Happens all the time to new Gantz fighters; Gantz provides basic pistols and a strength- and resilience-enhancing cybersuit to all new fighters, but doesn't explain why they're necessary, leading many to leave them behind in the room before being teleported to their first mission unless a veteran manages to convince them to do otherwise. Others take a gun, whose function is largely self-explanatory, and leave behind their suit, which is much more useful despite not looking like much. In the first arc, only Nishi (a veteran who knows what to expect) and Kurono (who observes Nishi doing so) wear their suits, causing them to fare much better than the rest.
- In the second arc, Kurono, not knowing that Gantz teleports its victims away from their daily lives to begin a new mission with very little warning, leaves his suit behind in his closet. Nishi, having more experience, wears his under his clothes at all times.
- Gunslinger Girl. Cyborg girl Triela runs away in tears after realizing her handler went on an assassination mission without her and got wounded in the process. She leaves both her pistol and conditioning medicine behind, and withdrawal symptoms make her too weak to defend herself when she gets grabbed by a couple of Camorra thugs.
- V for Vendetta: State Sec Chief Derek Almond confronts V at Dr. Surridge's house when V goes there to kill her but discovers too late that, while he did bring his gun, he'd left the bullets at home. Doubles as Laser-Guided Karma for him since he'd emptied the clip out earlier so he could threaten his wife with the empty gun.
- In the Discworld of A.A. Pessimal, the Pegasus Service employs witches who can commute around the world with the aid of the Feegle "craw-step" and winged horses, viewed as an upgrade on broomsticks. One such is Rebecka Smith-Rhodes, who works part-time for the Service whilst living in Rimwards Howondaland. While training as a Witch in Lancre, her Rodinian sponsoring Witch gave her a winter-wear outfit suitable for surviving outdoor work in a harsh winter. When Bekki moved to the Discworld's Africa, she reasoned she did not need to pack heavy-duty winter clothing and left this at her family home in Ankh-Morpork.. However, her Pegasus status obliges her to work part-time for the Service. Therefore, in January, she flies from Howondaland to Ankh-Morpork. to be craw-stepped right into the middle of the worst blizzards and sub-zero temperatures for twenty years. Her sponsoring Witch, who rescued her, is not pleased, and stands over her with folded arms while she recovers the winter survival clothing from home.
- In the Asterix animated movie Asterix vs. Caesar, Asterix has an argument with his best friend Obelix while attending a bath-house in Rome. He storms out while getting dressed, leaving his bottle of magic potion behind accidentally. He does not realize this until he is accosted by two Roman legionnaires, who promptly throw him in jail.
- Happens in Constantine when Angela leaves the protective amulet John borrowed for her safety in the car along with her jacket. This promptly leads to her getting captured by the heavy.
- In Crocodile Dundee, the titular character leaves his knife behind in the limousine just before he encounters a pimp he'd earlier decked. As things turn ugly, he reaches for it to find it no longer there, and only escapes being killed due to timely intervention by the limo driver.
- Happens in Deadpool (2016). Deadpool leaves the taxi to kill Francis and realizes he left his duffel bags of guns and bullets behind, leading to him only being able to use his swords. Then he does it again in the final battle, leaving a bag stuffed full of guns in the same taxi.
- While on the way to fire off the flares needed to destroy the title giant spider in The Giant Spider Invasion, Dr. Vance forgets the flares and needs to run back to the car and get them. Mike and the Bots immediately call out how dumb this was since it doesn't add any real tension and only pads out an extra 10 seconds or so of running time.
- Martin pauses, then leaves his gun in the hotel room as he leaves for the reunion in Grosse Pointe Blank — either because he's got a newfound respect for life or because he's in love with Debbie. He ends up having to improvise when the assassin finds him at the reunion.
- Hoffa (1992). Jimmy Hoffa borrows Robert Ciaro's gun while he waits in the car. Later Ciaro sees a hitman draw a silenced pistol on the unsuspecting Hoffa, reaches for his now-empty shoulder holster, then gets shot as he desperately rushes to save his friend.
- Inverted in Lockout: Hock, even when prison regulations insist that he leaves all of his weapons behind, stupidly decides to bring along an ankle-holstered pistol to Hydell's interrogation (and lies about it when asked if he gave all of his guns). This act gives Hydell access to the weaponry needed to stage a mass prison break-out, effectively dooming everybody inside.
- Pulp Fiction. Vincent is waiting at Butch's apartment to kill him if he shows up. While waiting, Vincent needs to go to the bathroom, so he leaves his Ingram MAC-10 on the kitchen counter. While he's in the bathroom, Butch shows up and uses the Ingram to kill the unarmed Vincent as he leaves the bathroom.
- Invoked in Sherlock Holmes (2009). Watson is furious when Sherlock leaves without his revolver, knowing he did it deliberately so his friend will feel obliged to chase after him.
- Left Your Lightsaber Behind is a running gag for Anakin in the Star Wars prequels.
- The Sure Thing. When Gib and Allison hurriedly leave the hotel room, Allison accidentally leaves her all-important planner (which contains all her money) behind.
- In The Treasure of the Sierra Madre Tim Holt takes away the insane Humphrey Bogart's revolver. He returns it only after unloading it. Bogart forgets to reload it and finds himself defenseless at the end.
- A Cure for Wellness. Lockhart takes a shovel with him while Exploring the Evil Lair but leaves it behind when running to hide because the caretaker is coming down the stairs. The caretaker sees the shovel and tries to kill Lockhart with it; later it's a Chekhov's Gun when the Mad Scientist chases Lockhart down there and his daughter uses the shovel to kill him.
- The Hitchhiker's Guide to the Galaxy: Played with in Mostly Harmless. Tricia Macmillian laments her boring life because a few years back she had the opportunity to go with a guy who was from another planet, but right after she went back for her bag, Zaphod left in his spaceship. She then used the mantra "Never go back for your bag." At the present time, she's running late for an interview as a prestigious anchor for a news program, and when she realizes she left her bag upstairs, doesn't bother to get it, citing her mantra. Later, she returns to her hotel room feeling horrible, having completely blown the interview, and goes straight for her bag, which has her contact lenses inside (without which made it impossible for her to read the teleprompter).
"As she dabbed each tiny plastic cup into her eyes, she reflected that if there was one thing life had taught her, it was that there are some times in which you do not go back for your bag and other times when you do. It had yet to teach her to distinguish between the two types of occasions."
- The non-fiction book by David Simon, Homicide: A Year on the Killing Streets mentions that detectives have to remind themselves to take their guns with them, as real-life officer-involved shootings are a rare event.
- Discussed in How NOT to Write a Novel as a possible way to handle any situation where a reader might think, "Why doesn't the protagonist just whip out their cell phone and solve the problem with one call?" For example, having a character not have their phone on them because they were woken by a fire alarm and ran out of the house is completely believable.
- In Masques, this is played with. Aralorn leaves behind her, unbeknownst to her, Anti-Magic sword when she goes off to fight the Big Bad. However, she didn't even know she would need the object, as she thought it was completely mundane and relatively useless. She is called out on it by someone more knowledgeable about magical things.
- Subverted in The Silence of the Lambs. When Clarice Starling goes to see Dr. Lecter in Tennessee, she has to turn over her spare reloader for her revolver. When she's discovered and rushed out, she leaves her reloader behind. If you noticed this, then during her final confrontation with Buffalo Bill, you were expecting her to run low (or out) of bullets, look for her reloader and not find it, and have to defeat Buffalo Bill with just One Bullet Left or an empty gun. In fact, she finishes off Buffalo Bill with several shots and then reloads.
- Slightly different example in A Song of Ice and Fire. While a group of people are escaping from Ramsay Bolton, with a plan that requires them to climb down the castle wall with a rope, they get discovered, and one of them decides to pull a Heroic Sacrifice You Shall Not Pass! on the guards chasing them to let the others escape. They go ahead and reach the top of the wall... only to realize that the person who stayed behind had the rope. Despite one of them bursting into hysterical laughter at the absurdity of it, this is very much Played for Drama.
- Mindstar Rising by Peter F. Hamilton. After completing a successful mission, Greg Mandel is ambushed on the way home. He grabs for his Armscor stun gun only to find it's missing and he realises he's no idea where he left it. Ironically it turns out the gun was stolen off him by his employer Julia Evans who was (incorrectly) worried Greg had changed sides, and she later uses it to save her life from The Mole who has sold her out.
- In the Blackadder the Third episode "Duel and Duality", Prince George is shot dead by the Duke of Wellington after a complicated switcheroo to avoid the prince being shot dead by Wellington. Moments later, the prince reveals that the bullet struck a cigarillo case he was holding over his heart, stopping the bullet. He then finds out that he left the case on his dresser, and promptly drops back dead.
- In the second season of Breaking Bad, when Jesse and Walt are being targeted by the murderous drug lord Tuco, Walt takes Jesse's gun and instructs Jesse to leave town after a brief argument. Jesse, defenseless, is held at gunpoint by Tuco and forced to lure Walt outside his house. Walt leaves the gun behind, something that causes Jesse no end of consternation when he finds out.
- In Season 2 of Stranger Things, when Bob Newby leaves the pistol Hopper gave him behind in a lower level of the Hawkins Laboratory and is subsequently killed by a Demodog.
- In the French-German mini-series Carlos, several French detectives go to question a "Peruvian playboy" photographed with a terrorist courier they've picked up for questioning. One detective goes to get his gun, but his commander tells him not to worry as it's just a routine checkup. Unfortunately, the so-called playboy turns out to be the terrorist Carlos the Jackal, who shoots them all dead in the belief they've come to arrest him.
- On Chuck when Sarah goes on a real date with Chuck she leaves her gun behind. They are then quickly captured by Michael Clarke Duncan and a bunch of mooks.
- Ultraviolet (1998). Mike Colefield rushes out to meet his Unrequited Love Interest, taking his pistol but forgetting the video camera attachment used to identify vampires. This causes problems when he starts suspecting she's a vampire but has no means of verifying it.
- Angel. In "Offspring", Team Angel page the title character to warn him about the Monster of the Week. The pager goes off in Angel's jacket... which is hanging on a nearby coat rack.
- Some GMs will pull this on players, claiming that if the player didn't specifically state that they were taking specific items. Such GMs frequently find that nobody is willing to play in their games.
- Parasite Eve has Aya go to confront the final boss right before another character would have given her the one weapon that could kill it. Since this character had a habit of giving Aya useless items there was no way for her to know that this one time, it was important.
- Shadowrun on the Sega Genesis has a double dose of this. The first quest in the game is to scrape together 250 nuyen so you can get your brother Michael's stuff out of storage - it may hold some clues as to why Michael was killed in a firefight. Once you get his stuff, you not only find a credstick for 500 nuyen, but also a Doc Wagon wrist band, which summons immediate medical aid once the user's vitals drop to dangerous levels (like during firefights.)
- On The Boondocks, the Freeman family goes to the movies and Huey brings along nunchucks because he expects it to be a disaster. Later on, he runs into the ushers while on his way to destroy the movie, and he realizes that he left his nunchucks on the sink after using the bathroom.
- As Mia prepares to head to Centopia in episode 21 of season 1 of Mia and Me, the camera calls attention to the fact that Mia's friendship ring has been left inside one of the gloves she was using while helping out with gardening. Naturally, this ends up causing trouble when Mia gets separated from her friends due to strong winds, since not only does she not have the ring with her, but because she doesn't have it, Yuko and Mo can't use their own rings to find her either.
- The Simpsons episode "Treehouse of Horror VI" has a A Nightmare on Elm Street spoof with Groundskeeper Willie as Freddy Krueger. After the Simpsons kids kill the evil Willie in their dreams, they go outside and an alive-and-well Willie gets off a passing bus and approaches them menacingly — only to start chasing after the bus because he says he left his gun on it.
- Star vs. the Forces of Evil: In "Death Peck", after accidentally provoking the subjects of the Pigeon Kingdom, Star is prepared to use her magic wand to escape. Unfortunately, she pulls out a stick instead, and realizes she accidentally left her wand at home while playing fetch with a brain-addled Glossaryck earlier.