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It Only Works Once
aka: Only Works Once
A one-shot cannon that needs one hour of warming up.

What may have worked ten years ago, no longer does!''

...and if it fails, too bad. You only get the one shot.

It Only Works Once is a method of defeating the bad guy which is completely useless in the following episodes. It could be a Forgotten Superweapon or other Applied Phlebotinum that cannot be replaced once it's used up. It might be an attempt to exploit an Achilles' Heel that the enemy will guard more carefully once it's brought to his attention.

Reversed, it is a common trope of cartoon series. The Big Bad will come up with some undefeatable plan that almost works save for some streak of luck on the part of the heroes (see the Road Runner shorts for some especially lucky breaks), but will never think of trying it again after being foiled the first time.

Occasionally a special attack that Only Works Once will end up being used in The Worf Barrage.

When you're getting near the end of a show or film and you know the trope will be averted because it's near the end and not a tragedy work, you're being Spoiled by the Format.

Never Recycle Your Schemes is a subtrope. Compare So Last Season, Forgotten Phlebotinum, Holding Back the Phlebotinum, No Plans, No Prototype, No Backup. See also Adaptive Ability, Reed Richards Is Useless, and the Disposable Superhero Maker. Most Wave Motion Guns apply a limited form of this trope by making its use prohibitively slow and energy-intensive, but the usual dramatic application is rather different. Often overlaps with Death or Glory Attack.

Examples

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    Anime & Manga 
  • The GeoGrey Sword in Digimon Savers; after its first appearance, it ceases to work on anyone, up to and including the villain in The Movie.
    • In Digimon Xros Wars there's the digimemories which have the data of legendary digimons, and can summon them to use their abilities. But they can only be used once for each zone.
  • Variation: Lelouch's mind control power in Code Geass only works once on any specific person. The duration can be permanent if worded correctly, but if the effect ends, that individual is never again affected by the power.
    • Unless Cyber-Jeremiah shows up with his Geass Canceler: the power alters their brain permanently, even if it only has any effect temporarily, but once the effect is reversed they're freed up to have it used on them again.
  • The Kido Cannon in the Bleach movie Memories of Nobody burns itself to ash after being fired only once.
    • Arguably, Ichigo's ultimate move the Final Getsuga Tensho, is this. Activating it will turn him into a Eerie Pale-Skinned Brunette Physical God since Power Makes Your Hair Grow, in Bleach; and use Mugetsu (Infinite Sky). This is at the cost of the Shinigami powers Ichigo has. As Ichigo himself says, that's why it's called the Final Getsuga Tnesho.
    • There's also Muramasa, main antagonist of the anime filler Zanpakutō Rebellion arc. Muramasa is a Zanpakutō spirit whose power is bringing other Zanpakutō spirits to life and turning them against their masters. He does this by tapping into their most suppressed instinct, and using it to control them. The only way to break the spell is for the Zanpakutō to be slain (which is difficult to reverse if it's by anybody aside from its master), but if they do, Muramasa's power won't be able to affect it a second time.
  • Straits in JoJo's Bizarre Adventure had the powerful Space Ripper Stingy Eye, an ability he witnessed in part one where a vampire can shoot fluids from the eyes at a ridiculously high velocity, allowing it to cut through flesh. The first time he fires it he misses a fatal shot at Joseph, but nicks his neck. The next time he tries it he hits a mirror reflection of Joseph and then the third time it is completely reflected, with Joseph lampshading that he only needed to see the attack once to know how to counter it, due to the predictability that Straits would go for the fatal shots in the neck and forehead again.
    • Subverted in Part 1 where Jonathan is caught off guard by Dio's attack of the same kind, as the first time it was used he was plummeting off a cliff and didn't see it firsthand. The second time it is used he had no idea it was coming.
    • Part 3's Anubis inverts this trope. Along with its unique traits, its skill in swordsmanship is so extreme that using the same attack twice against it is completely ineffective.
    • Later on in Part 7, during the climax of the D 4 C arc, Gyro uses the Super Spin Technique to attack Valentine. This attack rapidly ages cells to the point of death. Though technically successful, an imperfection in the steel ball cancels the perfect rotation, allowing Valentine to survive the attack.. Gyro doesn't get another shot. Johnny later attempts the same feat, but Valentine's warning prevents the Dio from another world from suffering the same fate.
  • The Gold Saints in Saint Seiya take pride in repeating how an opponent can only use a technique against them once, and then becomes ineffective. Their reasoning is that, having seen the attack once, they've learned how to avoid it. Sometimes the Bronze Saints are allowed to repeat this phrase, but only if their enemy poses no real threat whatsoever.
    • Only problem is that Seiya insists in using the same technique over and over, initially not hitting his enemy, but eventually it does and he didn't change his technique, he's just doing it faster.
    • Only SAINTS OF ATHENA have such a power or technique, as they learn to do it with their training. Seiya's case is always lampshaded as him going beyond the impossible to the point that his meteors are so numerous they turn into one big attack; cherry tapping up to eleven. Still, the dialogue fails to convey this realistically or seriously.
  • In One Piece, numerous villains seem to just give up after an ass-kicking by Luffy and co., despite the fact that they could logically resume their activities after the Straw Hats left the area. Especially since Luffy and company nearly never actually kill the Big Bad. Most of the time they go a ways to justify why the Big Bad doesn't do this, but occasionally they don't bother.
    • First example: Captain Kuro. Kuro had planned to leave a life of piracy by instilling himself as a butler of a rich child. After a few years, he was going to have his hypnotist force her to write Kuro into her will, then kill her and take her money. Instead he gets beat up and forced back out to sea. Though he couldn't have pulled this trick again on the same island (and would need to adjust the plan for a lack of a hypnotist), no one else knew he was alive and he could have tried elsewhere. Yet he's still a pirate as far as we know. Later it's revealed that the Marines somehow learned that Kuro had faked his death, though exactly how is unclear.
    • Next is Buggy, who had taken over a town. Luffy beats him and sends him flying. He could always just stay the course. However, Buggy being Buggy, he holds a grudge and starts following Luffy instead. This also happened to Alvida, who joined Buggy.
    • Crocodile looks this way (while his loss of Shichibukai status means he can no longer operate out in the open without drawing attention of the Marines, his criminal organization still exists), too, but a miniarc revealed that after Luffy defeated him, Crocodile lost interest in the outside world, which is why he didn't bother escaping with most of the rest of the officer agents. However, when he heard about the Whitebeard War, and when Luffy showed up on Level 6 too late to rescue his brother, he offered his power to help them escape, his interest rekindled by a chance to strike back at the pirate who ruined his dreams of becoming King. And with that pirate's death, he's ready to give it another shot; the last we heard from Crocodile, he was headed towards the New World again.
    • On the topic of Alabasta, there's Nami's Clima-Tact; Usopp had made it little more than a tool for parlor tricks, but the Tornado Tempo...what was it he said?
      "Okay, here's the deal: as long as your enemy is human, they won't be able to stand after being struck by it. But it's a last resort, and you only get one shot; if you miss, it's over."
    • Brook's devil fruit grants him the ability to come back from the dead...once. Since his soul took too long to find his body, he is now just a living killable (though arguably less easily) skeleton.
      • Arguably? With any risk of his body wearing out neutralized, he's immortal unless he's defeated in battle.
    • The Fighting King himself in Doflamingo's tournament. One hour of warm up = one punch. See the page image.
  • In the final episode of The Big O Roger Smith finally puts some of the pieces of the Myth Arc together and unlocks the Wave Motion Gun built into his mecha just in time to put an end to the Big Bad. Wouldn't you know: He missed, and firing the one shot burns the gun to a crisp.
  • Red Line: The president of Roboworld uses the Three-Point Disintegration Cannon to try to kill Funky Boy. Unfortunately, Funky Boy regenerates, while the Cannon needs two hours to recharge.
  • In a similar instance to the Saint Seiya example above, a Ranma ˝ OVA pitted (female) Ranma and Akane versus two powerful sisters.(never happened in the manga) After getting creamed in their first match, the two leads train for a rematch. The sisters' ordinary attacks then prove ineffective against Akane (who has trained up to their level) and their special skills are useless against Ranma (who explicitly says, "Your wind attack ain't gonna get me twice! I've seen it once and it's easier to avoid it!")
    • Turning the trope on the villain's favor, the manga confronted Ranma with the Musk Prince Herb, descendant of a dragon and master of chi techniques. When Ranma tried to use the overwhelmingly powerful Hiryu Shoten Ha technique on him, Herb recognized it and easily dodged it, since he had seen it many times before in the past and it was arguably part of his education. This was the same problem with Happosai, who had once been on the receiving end of this technique (from a young Cologne) and already knew how to thwart it.
    • Even further: when Ranma used the Parlay du Fois Gras technique on Picolet Chardin, it only worked for a few instants; both he and his teacher recognized the technique and immediately used a variety of defenses. Although Ranma tried to use new variations to get around these counters, each only worked once, until she was left with no way to attack her opponent.
  • Any Pokémon with the move, though most notably Ash's Torkoal, could only use Overheat once at full power. While the move could be used multiple times, it's power would be greatly lowered each time, generally resulting in this.
    • Roots in the game, where Overheat cuts the Special Attack by half when it is used. Naturally, this means that it should wipe out whatever it attacks, because the Pokemon will be useless for the remainder of its time out of the ball. This can be remedied by recalling it, but as that's the obvious move, the opponent will be able to predict you doing that.
    • A more extreme version would be Explosion; the Pokémon uses all its strength in a single strike, making it faint. A slightly weaker version is Selfdestruct.
    • Ash's Snivy's Attract only works once for an opponent. After that, they find a way to break through it.
  • Tengen Toppa Gurren Lagann. During their first encounter, Viral makes a point of telling Kamina sneak attacks only work once.
  • InuYasha:
    • Practically speaking, Miroku's Wind Tunnel. It should be able to instakill every enemy the troupe comes across due to its ability to suck everything into the pocket dimension in his hand, but it takes Naraku one encounter to learn how to neutralize it... which makes sense, considering he's the one who put it there in the first place.
    • Later, Sesshomaru discovers the hard way that the Tenseiga can only bring a single person Back from the Dead once.
  • Negi's Pactio in Mahou Sensei Negima! allowed use of all his partner's abilities and Asuna's antimagic (to an extent) but was merely used as a tool to keep Rakan from using his own Pactio. And after that, it was canceled. Obviously for the sake of drama (such a game breaker power) but seriously, you would think something useful like that would be kept around. Although he could easily regain it by making a Pactio with someone else.
    • No he couldn't. Pactios are the melding of Magister and Minister. Case in point: Setsuna has two different pactios at the same time, one through each of her Magister/Magistra.
    • He probably could. In the extras afterward, it's explained that it's rare to get multiple artifacts, like Setsuna did.
  • The Mafuba/Evil Containment Wave in Dragon Ball was able to seal King Piccolo away in a rice cooker in his backstory, but fails all three times it's used on him or his son/reincarnation:
    • Roshi tries to use it on King Piccolo, but it fails simply because he missed the jar.
    • Tien also planned to use it against King Piccolo, but in the manga practicing the technique broke the jar before he could even try. In the anime he gets a chance to try it, but Drum jumps in front of the wave himself and King Piccolo destroys the jar before Tien can even seal him.
    • Kami tries to use it on Piccolo (so he can stop him without killing him and thus himself), but Piccolo just turns it on him, mentally gloating, "If you thought this incarnation would be beaten like the last, then you have not thought!"
    • Likewise, it's revealed at the beginning of Dragon Ball Z that Shenron, and the Earth's Dragon Balls by extension, cannot grant the same wish twice; for example, if a person who has been already been resurrected is killed again, the person in question will be Killed Off for Real. Porunga, and the Namekian Dragon Balls by extension, have no such limitation.
  • Much like the Real Life example below, Zero no Tsukaima pulls this with the Wand of Destruction. Only Saito can use it, and it only works once. It's really an M72 LAW rocket launcher and it has one shot, so when Longueville aka Fouquet tries to use it on Saito, it doesn't work.
  • Human transmutation in Fullmetal Alchemist. That's because you have to give up your ability to use alchemy to do it, plus the person who you're bringing back has to be trapped at the gate (and thus not actually dead), plus your souls have to be linked so that you can return through their gate once you've given up your own.
  • In Naruto, played straight with Naruto's Rasenshuriken at first, and eventually averted when he overcame the dangerous side-effects of the said technique.
    • Izanagi, one of the Mangekyou Sharingan's powers lets the user cast an illusion upon himself making reality a dream and thus letting them escape life-threatening situations. However, the eye shuts permanently after it is used once.
    • Deidara's "ultimate art" C0 involves using himself as a bomb. Too bad for him, Sasuke had just made in advance an ultimate escape plan for such an occasion.
  • The Bartolls of the Super Robot Wars Original Generation OVA series worked on this trope - should an attack kill one of them, they would instantly adapt to it and find ways to dodge it or create ways to protect themselves. By the end of the second episode, Cybuster's forced to use CyFlash and the SRX is forced to use the Hyper Tromium Cannon just to wipe out a small army of them.
  • The Gravity Cannon, from Zoids: Chaotic Century, only had three shots available, one of which had to be a test-fire. It didn't work. A fourth shell is later created, it still doesn't work.
  • The Star Build Strike's shield, while not designed in such a way, ended up being this in practice due to the other fighters being very quick to learn. When its ability (absorbing energy from beam weapons and focusing it into either an attack or a boost in power) was first shown, it proved to be extremely effective. However, once everyone caught on to how it worked, it quickly became useless, as everyone he battled against would immediately focus on destroying the shield with physical attacks, thus preventing him from ever using it again.

    Comicbooks 
  • An Ultimate Marvel comic included Tony Stark curing Bruce Banner of the Hulk. The catch was that if the Hulk returned even once, its physiology could adapt and the cure would never work again. (See Doomsday, below) Predictably, by the end of the comic they are placed in a situation that requires the return of the Hulk.
  • In comics, the monster Doomsday (who once killed Superman) had "evolution" powers, such that he could adapt to counter attacks once used against him — i.e., having once been beaten by a Green Lantern's ring, he became relatively immune to its power.
  • Similarly, the DC Villain Calculator (before he was revamped as an evil Oracle equivalent) had an ability he'd use after each of his losses to a hero to "turn defeat into victory". He'd hit a button on his costume, which would render him immune to the powers of the hero who had just beaten him. Unfortunately, the DCU has an inexhaustible supply of heroes, so it never did him much good.
  • In Fantastic Four, many of Reed Richards' attempts to cure The Thing have been of the only-works-once variety. These always come with a reversal method which Ben will inevitably use, sacrificing his humanity to stop the villain.
  • This trope is used as an actual story element in Runaways. Nico's weapon, the Staff of One, can cast any spell whatsoever but then can never cast it again. (Attempting to repeat a spell results in random effects.) It essentially serves as a leash to her otherwise godlike Green Lantern Ring powers. However, it turns out that she can only use each specific spell with a specific code word once; in a team-up with the Young Avengers, she was able to cast the same spell repeatedly by running through the Vision's language banks.
  • In Paperinik New Adventures' fourteenth issue, a shadow creature can only be destroyed by a weapon created specifically for the job; the heroes, however, didn't have enough time to manufacture more than two charges for the weapon. As Paperinik puts it: "Be careful where you aim, you won't get a third shot."
  • The original 40s Captain Marvel once fought a character that could cast any spell - once. He also had one, and only one, weakness. Their fights consisted of the two of them flipping through notebooks that listed everything they had tried so far, trying to come up with strategies.
  • Spider-Man
    • This ended up happening by the eighth or so issue of The Amazing Spider-Man. In the Vulture's first appearance, Spider-Man took him down by simply clipping his wings with a device designed to cancel out the magnetic harness that allowed him to fly. Not so in their second encounter, where the Vulture puts in a fail-safe to get around this, and sucker-punches Spidey the minute he isn't looking.
    • Similarly, after being blinded with a squirt of webbing, Doc Ock started treating his glasses with a non-stick coating.
    • Spidey once came across Stilt-Man wreaking havoc. He was disappointed, as the villain had designed a mask to keep Daredevil from hitting him in the face with his stick. Spidey just webs him to a lamppost.
  • The Martian Manhunter once beat Despero with his innate Martian power to make someone believe that they're experiencing their most fervent desire. He'd never mentioned this power before and would never use it again, because, he explained, using it was so stressful that any one Martian could only do it once in their life. (Focusing on the pathos of his decision to use a power that his culture considered the ultimate gift to give a loved one to defeat a rampaging villain helped gloss over the Ass Pull.)
  • In an issue of The Uncanny X-Men Rogue absorbed Nightcrawler's powers and defeated Nimrod, the mutant killing robot from the future, by teleporting a chunk of his body away. The next time the X-Men fought Nimrod, Nightcrawler simply tried the same trick again, only to discover that Nimrod had adapted himself so that not only did it not work but the attempt messed Nightcrawler up quite badly. Thus proving that when it comes to Forgotten Phlebotinum, the line between Genre Savvy and Genre Blindness is whether it works.
    • Similarly, Sentinel robots in general had the ability to learn from experience (and transmit this information to other Sentinels), so a trick used on a Sentinel wouldn't work again on any Sentinel. Their ability to physically adapt to is more limited than Nimrod, so anything that beats a Sentinel through brute force will usually still work.
      • In Marvels Heroes Reborn arc Doctor Doom had guard robots that had this programmed into them.
  • Similar to the Doomsday example above, Marvel villain Ultron tends to come back whenever he's destroyed, now with immunity to whatever wrecked him the last time.
  • Doctor Strange once was turned into a vampire by Dracula, who boasted that since Dracula rules over all vampires, Strange was unable to attack him. Indeed, try as he might, Strange could no longer call upon his usual sources for spells: Aggamotto, Cyttorak, Watoomb, etc. In desperation, and with effort that nearly killed him, Strange called out the name of God.
  • Jimmy Olsen once discovered Superman's secret identity. At the end of the story, Superman used a combination of heat- and microscopic-visions, focused through a space jewel and directed through Jimmy's eyes, to burn out the portion of Jimmy's brain which held that piece of information. Superman lampshaded the trope by telling Jimmy that he could only perform this trick once: if he ever tried it again, he'd short-circuit his vision powers.

    Film 
  • Jack Sparrow's pistol in Pirates of the Caribbean. Guns of that era could only fire one shot at a time, and indeed the gun is only fired once during the movie. Technically he could carry extra ammo and reload (as Norrington observes), but for sentimental/plot reasons, he only carries one bullet.
  • Dodged around like an Old-School Dogfight in Star Wars, when the Empire makes a new Death Star that, when completed, will be immune to the tactics that allowed the destruction of the previous one—unfortunately, it's only half finished when the heroes get to it, and they simply have to repeat the same "single ship in a tight corridor" tactic inside the weapon to launch torpedoes into the core. That goes out the window when they find that the villains put up a force field around it. And the force field projector was heavily guarded. Sure, the Rebellion would have a shot if they destroyed the shield generator...but they weren't in very good shape. There's the indigenous population of the moon it's on, but they're just Ewoks, what could they... shit.
    • The tunnels leading to the center were likely a part of the whole design, something to make it enough of a target that the Rebels would actually go for it.
  • Godzilla:
    • In Gojira, the Oxygen Destroyer is a one shot weapon used to kill Godzilla, and its creator ensures that it can never be reproduced by destroying his notes and killing himself. In Godzilla vs. Destoroyah, however, the device turns out to have mutated dormant Precambrian organisms into another Kaiju, leading the humans to come up with an elaborate plan to lure Godzilla into a fight with it.
    • In the first of the films featuring Mechagodzilla, Godzilla was able to defeat his Evil Knockoff by tearing off his head, removing the controls and cameras that let the mechanical monster keep moving. The second time they faced off, Godzilla repeated the move, and was shocked when a second, smaller head emerged from the gap and blasted him with lasers.
  • In Tremors, each trick used to defeat a monster will not work on the next one, because the creatures are too smart and adapt just too damn fast. The trend continues to reappear throughout the sequels.
  • In Krull the seer known as the Widow Of The Web can protect vision seekers trying to enter her domain, in the center of a giant spider web, by turning over a large hourglass which immobilizes the giant spider guardian while the sands fall. We learn that leaving is impossible, because "it can be turned only once. That is the lure of the web."
  • In The Return of the King, Gandalf dashes out of Minas Tirith and saves the returning cavalry from death at the claws of the Nazgűl by firing a beam of light from his staff. In the director's commentary, Peter Jackson stated that he could not replicate the feat because his staff "ran out of batteries".
    • In the same scene of the book it was explained that it only worked because the Witch King, the most powerful of the Nazgűl wasn't present to counter his attack. Later in the movie, when the Witch King does show up, he breaks Gandalf's staff.
    • In the RiffTrax for the movie, the riffers turn it into a running gag with various soldiers and civilians trying to politely prod Gandalf to use that trick again as the Nazgul ravage the city.
    • The army of the dead only works once, as their oath is fulfilled after they have fought and they are set free. Although, in the film they are technically used twice: first to defeat the corsairs and capture the ships (they are set free after this in the book), then again on the Pelennor fields.
  • Richard Donner's cut of Superman II averted this trope by applying the same time travel reset button as the first movie, only in an even stupider way. More to the point, it links the freeing of the Phantom Zone criminals to Superman's use of this in the first movie tying into a warning Jor-El had given him about playing god with time. Superman did it the second time to fix the original mistake.
  • Back to the Future Part 3: Related to the Liberator Handgun below, Mad Dog has a gun that Only Works Once hidden in his hat and is foiled when Marty uses a Frisbee Pie Pan to deflect his one and only shot.
    • Derringers tend to be like that. The idea is to have a weapon-ANY weapon-when everybody thinks you have none. One shot is significantly better than no shots, and more complex derringers are harder to conceal. Derringers can be reloaded, IF you also smuggled in spare ammo for it. No time for that if your target is now aware you're gunning for him, and his buddy plus the town sheriff are within arm's reach.
  • The aptly-named "Henshin One-Shot" from the Non-Serial Movie of Kamen Rider Faiz lets a normal human henshin into Kamen Rider Kaixa exactly once. And that is because instead of the user suffering the after-effects, it dissolves the Kaixa Gear by overclocking.,
  • Tony's badass wrist-lasers in Iron Man 2. Justified when we see Tony eject a pair of smoking doohickies from his gauntlets after firing the lasers. The single shot clearly burns the doohickies out, leaving him physically unable to use the weapon again at the time. Since he doesn't grab a new pair of doohickies out of a storage compartment, we can assume that re-readying the lasers requires more than a simple doohicky swap. Doohicky.
    • Lampshaded by Tony himself when Rhodey says he should have led with that: "It's a one-off."
    • This is then averted in The Avengers in which Tony's new suit has retractable reusable wrist lasers that he uses more than once in the movie against much tougher enemies. In this scenario, the only thing keeping him from using them constantly is that they drain the armor's power something fierce.
  • In Man of Steel, the first time Superman and Zod fight, Zod's helmet gets broken and subjects him to Sensory Overload. By the time they have their rematch, Zod has learned to focus his senses.
  • Mentioned in Mud. Mud was bitten by a snake as a child and had his life saved by having an antidote administered in time. Unfortunately since the antidote is made of horse blood, it's something the body will recognize as a foreign material after being administered once and reject...meaning if bitten again there will be no way to save him and he will die.
  • The Amazing Spider-Man 2: During his first battle against Electro, Spider-Man hits him with water, defeating him. By the time Spidey uses the trick again, Electro had already figured out a way to create a barrier to protect himself.

    Literature 
  • Piers Anthony's Xanth series had the character Surprise Golem that had the magic talent of all magic talents. Her talent is to have whatever talent she wants at the moment. It was soon discovered she could only use each talent once, but she could achieve the same results by using variations. Which makes it not much of a limitation at all.
    • In 'The Dastard' Surprise finds out that she can perform the same spell twice with a significant period of time between the two only to have her discovery erased from time by The Dastard.
    • This is how all of the Adepts' spells work in Anthony's Apprentice Adept series, with the same variation loophole.
  • In Edgar Rice Burroughs' A Fighting Man of Mars, the hero obtains invisible items from the villain for some effect. However, they lose them. You see, the invisibility was always in effect.
  • In the New Jedi Order series of Star Wars novels, someone comes up with the brilliant idea of using the Centerpoint Station superweapon to destroy a Yuuzhan Vong fleet. Unfortunately the heroes get righteous on the guy trying to fire the weapon, and cause him to misfire. The weapon destroys a major Galactic Alliance fleet, and Centerpoint powers down, unable to be used ever again.
  • In John Varley's novel Millennium, once a time traveler visits a time, that specific time period from arrival there to return to your own time can never be accessed again.
  • In On Basilisk Station, we are introduced to the grav lance, which allows even a light cruiser to take down a superdreadnought's sidewall, but has a very short range, a quarter that of standard energy weapons. Getting it to work requires immense sneakiness and the enemy not looking out for it. It works the first time because the OpFor was not expecting it, but in subsequent exercises the other side knows how to look out for its attempted use. It is these repeated failures that get Honor the eponymous Reassigned to Antarctica. In the final battle against a Havenite Q-ship that outmasses even a super-dreadnought, she manages to pull off another successful use.
    • This is stated by Harrington to her students concerning her escape from Hades: the stunt she pulled to take out the State Sec convoy coming to retake the planet had so much that could have conceivably gone wrong, depended on the enemy being extremely sloppy in monitoring their sensors, relied on having detailed information regarding their approach that would be near-impossible to have in any other situation, and she had absolutely no other choice except to try it.
    • Subverted in Storm From the Shadows, as the Mesan plan involving New Tuscany is, and is Lampshaded as, a repeat of the plan used in Shadow of Saganami. However, the second attempt succeeds in its intended goal of provoking a war between Manticore and the Solarian League.
  • A version of a bluff that only works once in Harry Harrison's Invasion: Earth. When the crew of an alien ship threatens to drop radiation bombs on Earth cities, the military replies that they have a secretly-developed laser weapon trained on the ship. The aliens try to call their bluff, but their ship promptly explodes. Turns out there is no laser weapon after all, but the soldiers simply planted charges on it earlier (interestingly, no one mentions the problem of a ship filled with radioactive material exploding in Earth's orbit). The remaining alien ship, after a few more words, wisely decides to leave and not challenge the bluff.
  • Ender’s Game has a strategy winning a training battle that is discussed to Only Work Once (it is technically an exploit of the battleroom rules). It works. A similar strategy comes into play in the end battle, recalling that moment.
    • Ender is constantly challeneged by the teachers, who keep putting him in situations that prevent the use of old tactics, necessitating him to come up with new ones on the fly. Not only that, but the other armies keep adopting his tactics, so he can't use the same ones anyway.
  • Leprechauns in the Fablehaven series cannot be caught by the same trap twice. Patton Burgess not only caught one five times with five different traps, he had more traps ready for anyone who wanted to try it.
  • In William R. Forstchen's Union Forever, a large naval battle between the Cartha led by Cromwell's ironclad Ogunquit and the Roumans led by Keane's hastily-constructed ironclads is ultimately won by the latter despite the former seemingly winning moments before. Why? Because reinforcements arrive for the latter in the form of what appears to be a gigantic ironclad with three long-range guns that look like they could turn the Ogunquit into wreckage. In fact, it's a barely-working small single-cannon ironclad with bits of metal and wood attached to the front and sides to make it look larger and wooden logs sticking out to make them look like cannons. It's specifically stated that this trick will not work again.
  • This is a matter of some contention among the Lord of the Rings fandom, among whom there is a vocal minority that considers Aragorn's use of a seemingly invincible undead army in only one battle (rather than throughout the war) to be a Headscratcher verging on a Wall Banger. Debates about whether the Exact Words of their oath would have allowed him to demand longer service from them can (and have!) gone on for dozens of pages in various internet fora. The popular consensus is that the undead army was not magically compelled to obey Aragorn, but did so voluntarily as he was the only one who could release them to pass on to a more standard afterlife. If they'd gotten it into their heads that he did not intend to release them, they could very well have gone over to the other side, so he decided that it was better to be safe than sorry. YMMV on whether this explanation makes this a legit example of It Only Works Once or is merely a convenient bit of Fan Wank. Regardless, they demanded to be released after a single battle, and he complied.

    Live-Action TV 
  • The television series V was premised on this. The red dust which was all-powerful in stopping the Visitors at the end of the V miniseries was suddenly found to be ineffective in warmer climes. Also, re-application of the red dust wasn't an option since it was found that repeated exposures to the virus could be deadly to Earth lifeforms too over time (as opposed to instant death for the Visitors).
  • The "new" series of Doctor Who started its first season finale with Captain Jack Harkness using a gun with only enough power for one shot to disable a Dalek warrior.
    • However, he still uses it several times in "Journey's End" and "The Stolen Earth." Maybe he charged it back up...
      • The gun was originally a kitbash. He obviously had time to refine it and get it working properly in the two year interval.
    • Similarly, the power the Doctor gains over the Carrionites in "The Shakespeare Code" when he uses the species' name to banish one of them only works once. Oddly, though, it only works once AT ALL, rather than only working once on each member of the species.
    • Rose absorbed the Time Vortex in the season one finale, effectively making her a God, allowing her to reduce the Daleks to dust with a wave of her hand. However, the side effect was that it very nearly killed her, and caused the Doctor to regenerate after he absorbed the energy from her.
  • In Tomica Hero Rescue Force the team combine all their vehicles into Great God Striker and use it's Super Final Rescue to destroy the Big Bad Batsu. Unfortunately it fails.
  • In Star Trek: The Next Generation, the Borg have the ability to adapt to phaser frequencies after a few shots. The obvious workaround for this is changing the phaser frequency to something they haven't adapted to. The Star Trek: Elite Force games explicitly addressed this issue by introducing the Infinity Modulator (or I-Mod) gun, which changes frequencies too quickly for Borg to adapt.
    • In the first level of the second game (based on the last episode of Star Trek: Voyager), the Borg adapt to the I-Mod as well by using a jamming field specifically designed to stop the I-Mod from firing. The player is forced to do the mission with regular weapons, using shots sparingly.
    • The I-Mod actually infinitely randomizes the frequency to such an extent that the Borg can't even adapt to the randomization algorithm normally used by phasers.
    • In the series itself, much is made of this trope when anyone is simply planning on fighting the Borg. They know that any possible advantage they can come up with will result in the Borg adapting to render it ineffective quickly afterward. Thus, they often hold back the advantage until it is most likely to be needed.
  • Obfuscating Stupidity as a strategy in social game shows like Survivor. Part of the reason it only works once is that it relies on people not knowing who you are and only seeing the mask you put on in front of them. If say, you do this, get to the end or win, then return for an all-stars season a year or so later, your fellow players would know that you're not as dumb as you look. If you jump from one season directly to the next (such as Amanda&James, Rupert, Russell Hantz), then you'll still have the advantage of being unknown to your fellow players. That is, however, assuming the players are smart enough to see through it all. (Part of why Rob was able to get an easy victory in Redemption Island was because all his tribe members except himself and Kristina left their brains at home and thought Rob was going to take them to the finals.)
    • This was also Russell's downfall in said season. The first two times he played, he was unknown to the rest of the players. When he returned for Redemption Island, he wasn't put on the "Stupid" tribe and they saw him doing exactly the same thing.
  • Reaper had Sam, the main character, use vessels to catch escaped souls from hell. Each week's vessel was different, being an item related to what the escaped person had been sent to hell for.
  • In Power Rangers S.P.D., Kat is given a special Morpher that allows her to transform, but only has one charge. She takes it and goes into battle as the Kat Ranger for the first and only time. Note that, in Tokusou Sentai Dekaranger, Kat's counterpart, Swan, has different reasons for her Ranger form, Deka Swan, to be used. And she obviously shows up in Kaizoku Sentai Gokaiger.
  • In the first season of Workaholics, the guys got rehired after threatening to expose their boss' illegal business practices. This is never, ever brought up again, even in the numerous following episodes where she bullies them or makes their lives difficult in some way.
  • In an episode of Andromeda, the Nietzscheans are trying to erase the AIs of captured High Guard warships. They have finally created a device that can do that without any physical damage, and manage to delete the AI of the Wrath of Achilles. Dylan captures the device and keeps it in storage. A year later, a rogue AI named Gabriel hijacks a newly-built sister-ship of the Wrath of Achilles (Siege Perilous class), and Dylan uses the device again. However, Gabriel has been aware of the device's existence for this whole year ("For an AI, it's an eternity") and has managed to devise a countermeasure. To be fair, though, it would still probably work on any AI not aware of the device's existence.
  • Salem: For some reason, after Mercy's snake familiar is exorcised from her, she's now capable of staying in control of herself after Mary Sibley tries to put it back.

    Tabletop Games 
  • Most of a PC's powers in 4th Edition Dungeons & Dragons only work once per encounter or once per day. At least they can be recharged between fights, though...
    • For arcane or divine spells, this is justified by encounter and daily spells requiring a minute or two or longer of memorization, preparation, and/or prayer to prepare. For physical powers, it's explained that they are so physically demanding or reliant on surprise tactics that your character can only perform (or get away with them) once. This is one of the main reasons why there's a Broken Base over this edition: some players find that it's not airtight, but in most cases in works under Rule of Cool; other players find this a ridiculous case of Fridge Logic.
  • The GURPS Player Handbook suggests the DM should reward a clever player who comes up with a new gambit by letting the trick work ... but only once. The example given is throwing sand in an opponent's eyes to blind him — might work once, but if it were really that effective all the time, "fighters would leave their weapons at home and carry bags of sand instead." Thus to keep the game balance, creative gambits should only work once.
  • Champions. The villainous robot Mechanon has automated factories around the world. Whenever he's destroyed, one of the factories creates him again, this time with defenses against whatever destroyed him. This makes it much or difficult or even impossible to destroy him the same way again.
  • Almost every RPG is open to this trope. The GM probably had a pretty good idea of how you are supposed to get past a bad guy but either hinted at it too subtly, the players were point blank oblivious to anything other than violence or hilariously botched rolls while trying to figure it out, they just don't get there. And that means that the GM either has to murder all the PCs or let them lash together a plan between themselves to leapfrog this particular station on the plot railroad. But only this time.
    • Alternatively players being what they are, they may put in WAY more time and effort into working out how to defeat the bad guy from a Rules Lawyer perspective than the GM hoped, and thus arrive at a fait-accompli that is irrefutable from a rules standpoint but not what he had in mind. Given the effort involved, the GM has to let it pass this time, but threats (or possibly rocks) are likely to be passed should they ignore the plot and focus on breaking the system in future.

    Theatre 
  • In Wicked, Elphaba's control over her magic is limited, often gives unexpected results, and she can't undo a spell once it's been cast. This leads to problems throughout the story.

    Video games 
  • In Tales of Symphonia: Dawn of the New World, Emil's Mystic Arte Ain Soph Aur can be used on Richter the first time, but if you try using it again, he will counter it with a Mystic Arte of his own, magnifying its damage output and targeting your entire party.
  • The huge cannon you weld to your mining-vessel-turned-mothership in Homeworld Cataclysm has the problem of only working once - for some reason, energy conductors and heatsink systems suitable to power a cannon about 1/3 of the size of the entire ship were not included in the original designs of a civilian vessel. Searching for them is a major plot point taking up several missions.
  • In the second chapter of Disgaea, Flonne summons a dragon to attack you, announcing that because she has to use a special item, she can only do it once - thus, after she joins your party, there will be no dragon-summoning.
    • This can be partially averted... by capturing the dragon she summons, allowing YOU to summon the dragon whenever you want!
    • And then it's entirely averted... In Disgaea 4, where both Archeangel Flonne and Fallen Angel Flonne have it as a move, with the same incantation. The former summons a normal dragon while the latter summons a zombie dragon.
      • For a more literal interpretation of this trope, Bonus Boss Pringer X is this trope. Any special attack used against him will only damage him once. If you're fighting multiple Pringers, they all become to immune to the special move.
  • The Master Ball in Pokémon games, which has a 100 percent chance of capturing any Pokemon but only appears once in each game, which becomes especially frustrating in later generations as the number of stupidly-difficult-to-catch Pokemon increases.
    • Later games have it given out in the lottery but only if every number matches. So you can get more, it's just really really really rare to.
      • Black and White does not have a lottery, but did have a much easier way to get a second Master Ball. Simply participate in 50 online trades via the GTS. Unfortunately, this is no longer an option as the DS and Wii's online services (aside from the Wii Shop Channel) have been shut down.
    • And speaking of rarity, the Master Ball technically doesn't have a 100% success rate in all games; it's high enough that it doesn't matter, but it's not impossible for it to fail.
  • In Star Ocean: The Second Story, Claude uses his phaser beam (which the planet's locals call a "sword of light") to dispose of a beast attacking Rena. When he gets to the second town, he uses the phaser to break down a door, and it promptly (and inconveniently) runs out of power, and can never be used again.
  • To some degree this happens in Paper Mario 64 in the first (non-hopeless) fight with Bowser; his invincibility can be canceled out with the Star Beam you've spent the entire game earning. In the second a short time later, the move is now useless and you must get one better to win.
  • In the original Command & Conquer game, NOD only had the capability to launch a single nuke (it was a lot more powerful than nukes in the later C&C games though). GDI's counterpart, the Ion Cannon had no such limitations.
  • The call-in supertanks in Company of Heroes for the Axis factions, the King Tiger and the Jagdpanther. You get one per game, and God help you if Allied AT guns knock them out (and you don't have a Bergetiger to revive them). Then again, if the Allied players are still putting up a defense as opposed to screaming like a little girl, there's something wrong...
  • In Wing Commander: Prophecy, the protagonists capture an alien plasma weapon capable of destroying a fleet with one shot, install it to their carrier and successfully use it to destroy an enemy blockade. They then determine it would be too dangerous to try recharging it for a second shot.
    • Humorously described by one of the characters as "Fire and Forget. We fired it once, now we can forget about ever using it again."
  • In the original Metal Gear Solid, feel free to hide in a cardboard box right in front of the enemy. If they see you, they'll look at the box in confusion, then move on. However, if the same enemy sees that same box in the same place, he'll pick it up. Apparently, it's more suspicious for the box to still be there than for it to suddenly disappear.
  • In League of Legends, Poppy's ultimate ability, diplomatic immunity can turn out like this. Offensively, she uses it to take down an enemy champ without fear of repercussion from the rest (Unless they crowd control her and force her to waste it.) but once they're gone, she is immediately vulnerable and they'll likely get her down so she doesn't assassinate the rest of the team. However; it's fully possible for her to ult someone else, then wreak havoc without touching them, or declare Diplomatic Immunity in someone else and uses it to escape, which doesn't work just once....
    • Or any of the ap nukes, notably Katarina and leblanc, once you use up your whole nuking combo... you can only do small non-damaging auto-attacks. Good thing their cd are short, and katarina have her passive... This is why ap loses their powers late game.
  • In Quest for Glory IV, the ultimate joke is this. Anyone who hears it will laugh, no matter how little a sense of humor they have, but only the first time. You use it to distract the Big Bad long enough for you to kill him.
  • In Batman: Arkham City, each of the takedowns against Mr. Freeze only work once, as he'll adapt to them. You must find five unique methods of taking him down. In the higher difficulty modes, you have to figure out even more ways of taking him down.
    • In the comic book tie-in Batman comes up with the idea of disguising the Bat-boat as a fishing boat to sneak into Arkham City. It works brilliantly...until he tries it a second time, where the boat winds up blown up with a rocket. Lampshaded by Batman.
      Batman: That worked a grand total of once.
  • In Resident Evil Outbreak: File #2, you find an Explosive Leash control for the rampaging tyrant, which you can use to skip one fight with him. It doesn't kill him, though, and if you use it early he will return.
  • The console-only game (later ported to mobiles) Civilization Revolution only has one nuke in any single game. It's given to the player who builds the Manhattan Project wonder. It can hit any city or square on the map but leaves no fallout. Doesn't stop enemies from declaring war on you at the drop of a hat.
  • In Marathon 2, Durandal gets frustrated by this trope. He has a clever plan to introduce a virus into Pfhor war machines and turn them against their masters. It works... for about twenty minutes, before the Pfhor render it ineffective. Turns out another alien race called the Nar had that same idea twenty years ago, and the Pfhor have set up countermeasures against such tactics.
  • Chrono Trigger: After completing Robo's Quest and Lucca's Quest, Robo will offer Lucca a piece of Amber, which he'd made by compressing tree sap inside himself during his 400-year wait. The Amber is an Accessory, which grants the Auto-Life/Reraise status. It will work one time, and one time only.

    Web Comics 
  • In Cwen's Quest mysterious life slave Riddly Lancer defeats a huge dragon with an equally huge DBZ style blast. Next chapter when asked to do it again against to defeat the next bad guy he simply reports he can't do it again. Luckily he apparently has a few other skills.
  • In The Order of the Stick, Vaarsuvius make a deal with a trio of demons to become a virtual God-Mode Sue, but later claims that it can never be done again. This is probably true, since the demons have no reason to help now, but it is likely the real reason is trauma: while in power Vaarsuvius not only did some really nasty things, but nearly got killed due to overconfidence.
    • We don't know if they didn't have reason not to help her, the real problem is the other end of the deal which is giving the third-party villains time for which Vaarsuvius must serve them.
    • V wasn't saying the deal couldn't be made again, but was saying those spells couldn't be cast again. And they couldn't, since by that time the deal was finished, and Vaarsuvius didn't have the three spirits shackled to allow it anymore. Since they had been level drained repeatedly by then, it's possible the spells would be lost anyway.
  • In chapter three of The Adventures of Dr. McNinja, Dan McNinja defeats Frans Rayner by punching him in the right butt cheek and exposing his neckbeard. Years later, when Dr. McNinja fights him, Frans has moved his weak spot to a different location and taken extreme precautions to keep his beard from ever being noticeable.

    Web Originals 
  • An explicit theme of Fine Structure. Any given superscience technique will only work briefly before the Imprisoning God notices and changes the physical laws of the Universe to make it impossible.
  • Leet, a Gadgeteer Genius in Worm, has this as an explicit part of his superpower. He can invent a machine to fulfill any function...once. The second time it just explodes.
    • Crawler, a cape with an adaptive healing factor, becomes resistant and eventually immune to any form of damage he sustains and from which he regenerates.
  • Draugr, from The Saints, like other undead, have specific weaknesses. Unlike other undead, the quickly adapt and overcome those weaknesses.

    Western Animation 
  • A more straightforward Looney Tunes example would be the Bugs Bunny / Daffy Duck cartoon "Show Biz Bugs" in which he is trying to go one-up on Bugs in their stage act. When none of his tricks impress the audience, he desperately tries his ultimate trick: downing several kinds of volatile explosives and then swallowing a lit match ("Girls...better hold onto your boyfriends!"). The trope title is obviously the punchline to this gag.
    • The same gag was also used in "Curtain Razor" with a wolf trying to impress Porky Pig (which is a talent impresario in this short) with his act. In the end, the wolf gets his chance after several attempts, then doing the trick aforementioned, and as expected, the same punchline (kinda) is delivered.
  • The Kim Possible episode "Queen Bebe" and The Powerpuff Girls episode "The Boys Are Back In Town" both have the heroines confronting a previously-defeated opponent and trying what they used last time, only to find that it doesn't work anymore.
  • Subverted in Family Guy. Peter and Brian get rid of James Woods by leading him along with pieces of candy and trapping him in a crate. When he comes back later he steals Peter's identity they go through a long ordeal, but then Peter and Brian eventually get rid of him in the exact same way with Peter pointing out that they should have tried this again from the beginning.
    Peter: Okay, Brian, next time let's remember this right away because he's done this twice.
  • Subverted in The Simpsons where they try to get Maggie out of a locked bathroom. Homer tries a coat hanger then gives up. Lisa tries to Coat Hanger again, successfully unlocked the door and lampshaded that why they only tried it once anyway.
  • Both used and subverted in The Batman episode "Meltdown". Batman first defeats Clayface by throwing a freeze-bomb at him. When he tries it later, Clayface said he saw it coming and just made his body hard so it bounced off. Then Detective Yin does this after pretending she was going to shoot him which prompted the line:
    Clayface: Didn't expect that from you Yin. I guess you do have... a new partner.
  • Something similar happens in Batman Beyond. Inque was vulnerable to freezing and water in her first appearance, but in later appearances learned to curl herself into a ball, protecting the bulk of her mass from being frozen and breaking free in short order, or modifying her chemical makeup to resist water. Batman himself uses this against Inque, protecting himself from being enveloped by her with an electricity based contact defenses.
  • The Spectacular Spider-Man: In the Villain Team-Up episode, Doc Ock explicitly points out that none of the methods Spider-Man used to stop his foes last time will work: Doc Ock's arms are powered by Electro, the power pack on Vulture's back is better armored, Electro has much better control of his power (such that he can safely contact water), Shocker and Rhino know better than to confront him in an enclosed space, and um...there aren't any concrete mixers around. It goes both ways, though, since Spidey's also been upgraded since the last time he fought them.
  • Superman: The Animated Series saw the Man of Steel use this trope frequently. When his foes escaped from Cardboard Prison, they'd usually find Superman wearing a suit designed to be proof against their powers. Somewhat subverted, though, in that these suits were not foolproof and the villains found ways around them (or just ripped them off).
  • Mojo Jojo tries to avert this in an episode of The Powerpuff Girls by trying an old plan a second time, thinking he's taken precautions against what ruined the plan the first time. The girls defeat him anyway, showing that maybe it's best to turn your back on plans that have already failed once after all. Considering that his precaution was to not turn the girls into dogs, thus preventing them from biting his butt (now protected by a metal plate, one would think that doing either of those things cancels out the usefulness of doing the other, but whatever) and making him break the magic idol he was using, they weren't very good precautions. He forgot that, since the girls aren't transformed, they can foil his plans in the same way they foil all his plans; by beating him up.
  • After The Flash defeated Brainthor in Justice League Unlimited by tapping into the Speed Force he said he didn't think he'd come back if he went that fast again. Notably, when another version of the Flash in the comics did something similar, he didn't come back.
    • Doomsday's Justice League incarnation had the same abilities as his mainstream self.
    • Amazo was able to adapt so that the kryptonite didn't work on him.
  • On an episode of The Adventures of Jimmy Neutron: Boy Genius, the title character builds nanobots in a flying saucer to defend him from bullies. They malfunction and begin to threaten everyone who comes within 5 feet of him. He defeats them Logic Bomb style by beating himself up. Take 2: Jimmy re-hires the Nanobots as Beta Readers for his homework assignments, and they take their "correcting errors" to extremes, going so far as to start correcting human error (bad posture, fashion, etc.) He tries to Logic Bomb them again by saying that flaws indicate that humans are functioning perfectly, but they stop trying to puzzle it out, call it "extreme error" and just start deleting people off the face of the earth. Somewhat subverted, though, in that he still uses their programming to overload them; he purposefully miscalculates a number on his homework, and asks the nanobots to correct it. The number in question? Pi, which no computer could calculate to perfection.
  • In Titan Maximum, Palmer believes that his favorite move, the Sucker Punch works every time. However his brother Billy, points out that attack can only work once in each fight because it is quite impossible to catch the guy off guard again.
  • A Gumby cartoon had Gumby returning a wand to a magician who left it behind at Gumby's lemonade stand (it made sense then). The magician rewards Gumby with a wand that will perform a single trick. Gumby uses it to repair his mother's pitcher that got broken at the start of the cartoon.
  • The Lich from Adventure Time is a master of this. If its beaten him once, he'll make sure the heroes don't get a chance to use it again. First off by destroying Billy's Gauntlet before Finn can use it against him. Followed by swatting Finn away while possessing Princess Bubblegum before he can use his "Like-Like Sweater" to destroy him. And as of the season 4 finale, killing Billy, the one who imprisoned him in amber. Notably, it's not because he gets stronger in-between attempts, he's just really good at planning and manipulation.

    Real Life 
  • Early firearms (prior to the mid-18th century or so) worked like this in ground battles. Sure, you could reload them... but it took so darned long (1-3 minutes) and the ranges of the weapons were so short (50-100 yards) that you'd be lucky to get off two (somewhat inaccurate) shots in the time it took for an enemy (on foot) to come within range, charge and attack you with something sharp and/or pointy. Bayonets were developed so that muskets could double as melee weapons, eliminating the need for pikemen. Contemporary hand grenades (thus Grenadier units) and rockets - like those used in China - only worked once.
    • Still musketeers and other gunmen usually carried somewhere between 8 and 16 reloads on their person (their flasks with gunpowder were known as "12 apostles", despite there not always being 12 of them). On top of this, there would be carts with more powder and bullets behind the lines. While some generals really liked charging to within range, having to run through the salvos of bullets usually meant the charging formation was in worse shape than the one being attacked by the time they arrived, and stood a big chance of losing the subsequent "push of pike". So it was more common to try and destabilize the enemy formation by firing at them yourselves and by sending loose skirmishers, cavalry charges and cannon fire at them, before actually going in for the melee. So most of the time, this trope was averted. There is a reason these firearms were used. Still, a rush could succeed if performed so fast that the enemy had no time to get ready for the hand to hand. This tactic saw a short period in the limelight after the invention of the plug bayonet, which had to be plugged into the barrel of the gun, and could therefor not be mounted before going into battle.
  • The Liberator handgun. It was possible to reload them, it just took a long time. They were nearly useless as weapons, the lack of rifling meant that the bullets would sometimes strike sideways and bounce off of people if fired from more than a few feet away. The were good for super-short range kills, though — if the attacker could get within a couple feet they could be effective. The general idea was to use it to take out an occupying soldier and take his gun. And more importantly from the Allied perspective, to demoralize the enemy with the fact that they have no idea just how many are out there, and how many of the seemingly helpless civilians in conquered nations are actually armed.
    • The same applies to The Vietnam War-era replacement, the Deer gun, though its effectiveness as a weapon was never determined; when the war escalated, plans to hand the gun out to civilians in the same manner as the Liberator were abandoned.
    • The "Punch Gun", made famous in Inglourious Basterds, is a real gun that only works once in concept. Because you have to hit your opponent to "pull" the trigger, it would be hard to not kill him. But if he has buddies around, you will be in for a rough time.
  • The tactics the 9/11 hijackers used to seize control of the planes fall into this category. Generally speaking, since most passengers in previously hijacked airliners did in fact survive, there was no reason for passengers and crew not to cooperate.note  Now that using the plane as a kamikaze weapon has been firmly established as a possibility, trying to take over a plane with knives will likely not work because the passengers and crew will fight back and overpower the hijackers.
  • The M72 Light Anti-tank Weapon, its modern successor the AT-4 and various similar designs based on the same concept. Though arguably they're a subversion, as theoretically they provide the reverse effect in practice; instead of having a dedicated RPG fireteam, who have to spend precious seconds reloading after taking a shot and can't carry a hell of a lot else besides the launch tube and its ammunition, every man in the squad can carry a one-use launcher as part of their regular gear. If one of them misses, another steps up and takes their own shot.
  • Successful suicide bombing.
    • Likewise, if you botch the bombing such that you don't die but the target knows your intentions, they'll likely try their damnedest to kill you.
  • The Trojan Horse gambit - anyone with even the most cursory knowledge of military history will know better than to fall for it. It even spawned the phrase "beware Greeks bearing gifts".
  • The Eastern variant was Zhuge Liang, who, when faced with 60:1 odds in a battle, he sits himself on the parapet above the gate to play the lute with the gates themselves flung wide open. Due to his well-deserved reputation, the opposing general retreats rather than risk getting lured into a trap - and it fits squarely into this trope because the only reason it worked so well was due to it being the first time Liang had ever bluffed.
  • One of the poetic metaphors for a woman's maidenhead (or, more generally, virginity) is, "the rose that can be given only once".
  • Medical examples:
    • The arsenical medicine melarsoprol, used against African sleeping sickness, is extremely toxic. So toxic in fact, that it can't be administered to someone who's been dosed.
    • The precordial thump is a sharp punch to the sternum sometimes attempted during CPR. In real life, it's never done more than once — not only is it risky, there simply isn't time. The thump has to be performed within 60 seconds of the onset of symptoms. (In fact, according to one study, all reported successes have been within ten seconds!) Basic CPR training no longer includes it.
    • Cats do not have antibodies for dog blood cells, so if no feline blood is available an injured cat can receive canine blood instead. However, within four days the cat will have developed said antibodies and can never receive dog blood again without suffering a severe (likely fatal) reaction.
  • Ceramic trauma plates for body armor. It can only reliably absorb one, maybe two bullets before it breaks and you have to bolt for cover. On the upside, their ballistic value is generally much higher than traditional metal trauma plates.

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