So you've got a hero. He's a really good hero, and he has rules (heroes often do, after all). Let's say, hypothetically, that one of those rules is that he'll never use a gun. Maybe his parents were brutally murdered in front of him with one, spurring him into heroism in the first place. Whatever. The guy doesn't use guns.
Then something bad happens. The stakes go up. Maybe a villain bent on bringing about universal entropy arrives. The hero's pushed to his absolute limit. The world, even the universe, is hanging in the balance. There's only one way to put things right. The hero picks up the weapon...
Batman's Got a Gun.
Can, and often does, overlap with Let's Get Dangerous, Big Damn Heroes, Out-of-Character is Serious Business, and/or Despair Event Horizon. It's a kind of Godzilla Threshold. Pretty much always results in an Oh Crap moment for the villain. Can be a Moment of Awesome, but it will always be Played for Drama. This trope isn't just a hero doing something they wouldn't normally do. It's a hero doing something they're fundamentally against (see the examples below). If the hero has ever done it before (at least, during their heroic career), it's not this trope. This is the hero breaking their golden rule.
When adding examples, please be sure to mention for the sake of clarity what the rule is that's being broken.
- Trigun: Vash uses guns all the time. However, as a master of Improbable Aiming Skills, he uses it solely for trick shots, and when in serious trouble, will at most shoot a person somewhere where they'll heal. He doesn't believe in a situation where you can't save everyone. However, at one point, he is given a true no win scenario, where the villain sets up a situation that will result in the death of his friends, unless the villain is killed (he has... issues). After much hesitation, Vash kills him. He doesn't take it well. Bear in mind that this was merely The Dragon he killed, and getting himself shot was the whole point.
- Miria in Claymore breaks her one rule of never killing fellow Claymores during her battle against Hysteria the Elegant, as that was the only way to end the fight before a recently Awakened Cassandra killed all her allies.
- Neon Genesis Evangelion's Shinji has always kept the same promise to himself to "never run away" from his duties for 26 episodes, and aside from a couple stunts, he always came back. He only broke down when everything else fell apart in the Movie. Come Evangelion 2.0, he was ready to smash up his personal base after one too many mistakes. Hell, he was ready to ignite The End of the World as We Know It against Zeruel when he was able to cope with it the last time he saw him. It was only thanks to Kaworu, aka. Tabris, aka. Shinji's guardian angel to stop him from a Rage Quit.
- Monster: One of the major theme of the manga is the mental and physical tribulation of Dr. Tenma as he's forced to pick up a gun to hunt and kill a monster he unknowingly saved. This trope already has a bleak atmosphere hanging around it, but it's pushed to the realm of Deconstruction in his case. In the end, he didn't kill anyone. Not even The Dragon of said monster he thought he killed. Not the monster himself, the final confrontation with whom put the life of a child at a stake.
- Fullmetal Alchemist: In his battle with Wrath near the end of the series, Scar breaks his code as an Ishvalan and uses Alchemy to reconstruct matter, thus regaining the upper hand. Up until that point, he only used his abilities to destroy things and so remained technically within the bounds of his code against it.
- The Trope Namer: Batman breaking out a gun as his "once in a lifetime exception" to try and kill Darkseid during Final Crisis.
- There are numerous counter-examples (his 1939-1940 version (now out of continuity) used a gun occasionally, and there are isolated stories here and there where he uses one as a threat or a tool), but as far as the spirit of the trope goes, Final Crisis is the only current in-continuity example of Batman using a gun with intent to harm/kill and going through with it, and even the current page image from Batman: Year 2 had him not go through with it in the end thanks to circumstances outside of his control. In the previous Crisis, when Alexander Luthor Junior nearly killed Nightwing, that was the last straw for Batman. He grabbed a nearby gun and was fully prepared to kill Alexander for everything he had done up to that point until Wonder Woman convinced him to back down.
- Daredevil attempted this after Bullseye killed Elektra, but Bullseye survived.
- In a later storyline, Daredevil takes the same gun (a silver-colored revolver) and almost uses it to kill himself after Bullseye murders Karen Page.
- Daredevil finally killed Bullseye after the latter blew up a housing project killing everyone inside. Daredevil was also a bit demonically possessed at the time.
- Dick Grayson broke his no-killing rule after he believed The Joker had murdered Tim Drake.
- Pretty common in general among the Gotham heroes, as it happened with Catwoman against Black Mask.
- Two-Face had a villainous one a long time ago, choosing to ignore his coin to spare Batman's life.
- Superman generally never uses his heat vision against living beings. Except against Mongul in For the Man Who Has Everything. Burn, indeed.
- He finds himself forced to execute Kryptonians of a "pocket universe" after they have killed almost everybody in their universe. This experience eventually causes him a breakdown.
- In Superman: At Earth's End, a power-less Superman uses guns without blinking. (Just another reason why it's been said that said comic is "Superman In Name Only")
- An aversion in the final issue of Richard Dragon's series. He's sworn off killing, and SPECIFICALLY sworn off using the deadly Leopard Blow, but resolves to kill one final time (specifically, to kill his love interest/arch enemy Lady Shiva) to save the life of a young boy. During the climactic battle with Shiva, he has her set up for the blow, and attempts to deliver it, but is tackled away by her ninjas and killed shortly thereafter.
- It is worth mentioning that large parts of this series have been booted from canon.
- Captain America, who, being The Cape, embodies values like Thou Shalt Not Kill has found himself forced to kill his enemies sometimes:
- He had to decapitate Baron Blood because it was the only way to stop a vampire. Cap was crying when doing it.
- To save innoccent lives, he killed an ULTIMATUM agent. The memory still haunted him when he faced ULTIMATUM again.
- In the 1980s there was a story that found him shieldless and witnessing terrorists seconds away from opening fire on innocent civilians. Without a weapon and knowing he could not make it to them in time, Cap grabbed a discarded machine gun and opened fire.
- When Cap and Bucky Barnes first appeared, they used guns all the time since it was a different time. When he was brought into the Silver Age, they gave him a Retcon, explaining that he never used a gun or lethal force, even during the war. More interpretations explain that Cap used guns during World War II but has since avoided using lethal force. As Cap sees it, he's no longer acting as a soldier, so using lethal force isn't appropriate.
- Subverted during an arc of X-Men: Professor X, of all people, is packing heat. But it's only to use as a last resort on himself to prevent any evil force from "hijacking" his brain (arguably one of the greatest weapons in the Marvel Universe). When faced with such a threat... he does not go through with it, giving the entity a chance to leave his mind before he fires. Things go downhill from there...
- Spider-Man in the Back in Black arc nearly fits this trope. After Aunt May is shot by a hitman Peter flips out and dons his black costume. He goes around the town beating people to hospital until he finally meets the main villain, Kingpin. If Kingpin had a fair chance against Spidey during the 1970s and 1980s, we don't see it here, its Curb Stomp all along. In the end Kingpin is left bleeding and broken with a promise, if/when May dies, Kingpin will follow. There is a What If... story where MJ takes the bullet and dies. In that story Pete goes on full rampage and in the end punches Kingpin through the heart. Try to remember, this is from friendly neighborhood Spider-Man.
- Peter had inadvertently killed in the past: the second Red Skull who had killed his parents (he redirected a missile which ended up killing him), ducking out of the way of Norman Osborn's spiked glider which pierced his heart (although he got better), he backhanded a Badass Normal terrorist and killed her when in battle against Wolverine (he thought it was Wolvie in a berserker rage), and killed Morlun in an evolving nigh-animalistic state during The Other storyarc.
- ROM Spaceknight usually follows Thou Shalt Not Kill, but made an exception for Hybrid when he realized his Neutralizer couldn't banish a human-Wraith hybrid to Limbo and that Hybrid was too evil and dangerous to be allowed to live.
- InHigh Noon, Amy Fowler (Grace Kelly), a devout Quaker, comes to the rescue of her new husband Will Kane (Gary Cooper) when she shoots one of his enemies from behind, violating her pacifist beliefs in order to save Will's life.
- In Things to Do in Denver When You're Dead, protagonist Jimmy the Saint spends the last twenty minutes or so of the movie doing all the things he spent the whole movie trying to avoid doing.
- In Wizards, Actual Pacifist wizard Avatar confronts his evil brother Blackwolf, and rather than engage him in a Wizard Duel, simply pulls out a gun and shoots him dead.
- In The Rundown, the Rock's character refuses to pick up a gun the entire movie, maintaining that "bad things happen" when he does. When he gets into a tight spot in the end, he does end up using guns—and it's awesome.
- In Unforgiven, William Munny avoids drinking because his wife "cured" him of such vices before she died. When Little Bill kills Ned, Munny finishes the Kid's bottle of whiskey and goes on a Roaring Rampage of Revenge.
- Any time a Harry Potter protagonist uses an Unforgivable Curse: Professor McGonagall with the Imperius Curse, and Harry himself using the Imperius and specially the Cruciatus Curse.
- In The Dresden Files, Harry has been offered incredible power, often at terrible prices, throughout the series. He's always refused, though at the same time has always been tempted by that power. Offers range from the addictive draw of pure Black Magic, the eternal knowledge and power of a Fallen Angel, the possible godlike power of the Darkhallow, and the standing offer by Mab, Queen of the Winter Court, to become her Knight. Harry steadfastly resists all of these offers, as he knows that succumbing to these temptations will destroy him as a person. Then the badguys kidnap his daughter, and Harry accepts Mab's offer to become her Knight.
- Earlier on, he threatens to pull everything listed above to his advantage if Mavra the Black Court Vampiress ever does harm to his friends again (especially Murphy). The threat is so effective that Mavra hasn't been seen or heard from since.
- Famously done in Magnum, P.I. with Magnum shooting an unarmed man.
- In Doctor Who, the Doctor has had a few of these moments (at least as far as the taking up; mostly he's never gone all the way through with the using it):
- In "The Invasion of Time", he not only takes up a gun after Gallifrey is invaded, it's an ancient Time Lord superweapon he builds from scratch for the express purpose. And he uses it, after the leader of the invaders forces his hand.
- In "Revelation of the Daleks", the Doctor takes a gun and sets out to kill recurring villain Davros.
- He does the same thing in "Resurrection of the Daleks".
- In "Dalek", the Doctor threatens a Dalek with an alien weapon in an attempt to prevent it from escaping the Elaborate Underground Base.
- The Tenth Doctor takes up a gun in "The Doctor's Daughter" and aims it at the general who just shot his 'daughter' who took a bullet meant for the Doctor. However, he puts it down at the last minute, instructing everyone else that "he never would" and they should choose a leader who never would, either.
- In The End of Time, there are several scenes where the Doctor flat-out refuses to take Wilf's old Webley revolver in order to stop The Master. However, he grabs it in a heartbeat when he learns that the Time Lords are returning. And he uses it, too, but only to destroy the device allowing them to escape the Time War.
- The Eleventh Doctor takes a soldier's pistol in the climax of "The Time of Angels." However, he only uses it to destroy a Gravity Globe and engineer an escape from the Weeping Angels.
- Leverage: Elliot Spencer does not like guns. He never said he couldn't use them.
- White Collar's Neal snaps in this manner when he has a chance to encounter and kill the man who he believes killed Kate. All of his friends are so worried about him being in this state that when Mozzie finds out he's got a gun, he immediately calls Peter, an FBI agent, which is his equivalent of this trope.
- Buffy the Vampire Slayer Doesn't Like Guns. She thinks they're not helpful, she has terrible aim with them and has a vested interest in not involving gunplay, not the least being one of her best friends and secret confidant was killed with a gun. Her normal reaction is to either advise not to use guns or to dispose of them. Nonetheless, she can and does use them. A rocket launcher against a demon (or to try and kill the school principal/Slayer's son/future love interest when he suspends the boy she's currently keen on), threatens another demon with his own rifle, and arms the Slayers to fight an army.
- Faith from Mirror's Edge applies to this; considering her parents were shot for protesting, her sister is a cop and the player is generously awarded for not so much as shooting anyone, you know Faith is pissed when she's pointing a gun at an officer.
- Played with in Metal Gear Solid 4: Guns of the Patriots, with Snake's rule not to use CQC (added to the series in Metal Gear Solid 3: Snake Eater, a prequel, so presumably Snake knew it since before Metal Gear), because of Big Boss' betrayal of FOXHOUND. He uses it because his first response to someone using it on him is to respond in kind. While Liquid, Ocelot, Gray FOX and Solidus might have known it, they all either had their own highly effective fighting styles, or were just never never in a situation where they would use it.
- Played brilliantly straight in Devil May Cry 3. Dante and Virgil are twins who are the sons of the demon Sparda. Dante chose to fight against demons, despite being half-demon himself, while Virgil joined them. Dante uses his pistols, Ebony and Ivory, and his sword; Virgil only uses his katana, Yamato, hating guns because he believes them dishonorable. However, when push comes to shove, Virgil ends up taking one of Dante's guns and the pair shoot Arkham simultaneously, finishing him off.
- Sort of in Mass Effect 2, in the Overlord DLC. Paragon!Shepard isn't completely averse to violence, but tends to keep it as a last resort. Later in the mission, there is a paragon interrupt to pistol whip a Complete Monster because of his Moral Event Horizon, not in self-defence. And it's awesome.
- Batman Beyond is kicked off when an aged, ailing Batman suffers a heart attack at the worst possible moment—right in the middle of a crime bust—and is forced to grab a gun to defend himself. This Moment of Weakness convinces him that it's time to hang up the cowl, setting the stage for Terry to take it up years later.
- The Justice League Unlimited episode "Dead Reckoning" has Deadman possess Batman and kill Devil Ray with a nearby gun in order to save Wonder Woman. Batman is visibly disgusted with it.
- Batman: The Brave And The Bold plays with this in the Grand Finale. Bat-Mite, trying to get the show cancelled, alters the show dramatically with many Jump the Shark mainstays, while Ambush Bug tries desperately to prove to a disbelieving Batman that it's not right for him to have a wife, a sickeningly cute daughter, and obvious toy tie-in gear. He finally gets Batman's attention when Bat-Mite makes him use guns, which Bug points out is completely Out of Character for Batman, and this makes the turning point of the episode where Batman starts fighting back as well.
- Based on her personal politics and ignoring player cruelty potential