There are some characters who fight for glory, or to atone for their past deeds. Some of them don't really want to survive. Then you've got all the heroic motives - For Great Justice, for friends, for society, the list goes on.
And then you've got this guy.
He'll be right in the thick of the battle, laughing his head off, and genuinely enjoying himself. Whatever the reason, he's simply enjoying the fight. This can be downright creepy.
Like the character who displays Dissonant Serenity, the one who pulls off Dissonant Laughter is very definitely at odds with the world around him, although, rather than contrasting chaos with calm, they will contrast the grim battle with their lightheartedness.
The nature of the laugh is not important, either - it can be maniacal, like the Laughing Mad, a mildly psychotic chuckle, whatever the character feels like at the time - so long as it's because they're having the time of their lives.
- There's a lot of this in Baccano!, mostly on the parts of Ladd Russo and his buddies. The most dissonant example comes from Dune, who giggles maniacally as Claire Stanfield dangles him off the caboose of a moving train and grinds his arm to bits against the tracks.
- Some of the Biological CPUs in Gundam SEED and Gundam SEED Destiny.
- Donquixote Doflamingo of One Piece is pretty much always seen laughing, or at least grinning widely, even as he forces people to fight each other to the death, among other things. This is cranked up even further during the war with Whitebeard, where he reacts to pretty much everything with psychotic laughter.
- Soul Eater's Franken Stein starts laughing at his craziest, notably when facing Medusa, and it's pretty alarming. Even when not at his craziest, he sometimes sports a wide grin while beating the crap out of people. And he's a good guy... on most occasions.
- Bleach: Only when Zaraki Kenpachi's life is in genuine danger from an extremely dangerous foe does he enjoy the fight enough to laugh.
- Kemonozume has Ooba who is obviously completely insane but is obviously enjoying himself immensely and is often seen chuckling or laughing like a maniac.
- Whenever Higurashi: When They Cry's Shion is the "crazy one" she's prone to this. After she kills Satoko, shortly before remembering Satoshi asking her to protect his little sister, she snaps and is laughing even harder. Even while falling off the roof of a building.
- Tsuruya of Haruhi Suzumiya is The Hyena and has laughed, serious or not, for everything, practically.
- Scorpio Kardia in Saint Seiya: The Lost Canvas. His opponent Wyvern Rhadamanthys is not amused.
- Shin Kazama does this in the last issue of the Area 88 manga. After witnessing the deaths of Saki, Mickey, and Sela, Shin is so emotionally overwhelmed that he starts laughing hysterically. His laughter makes Kim extremely uncomfortable. He returns to his senses when Kanzaki contacts him.
- In Puella Magi Madoka Magica, Sayaka Miki begins to laugh and smile during her battles as a result of her effectively becoming a Death Seeker as she lets her Soul Gem darken. She also giggles insanely during one of her special attacks in the PSP game.
- Togepi from Pokémon will often laugh even when things go south. Then again, it's probably just easily excited considering it's a baby.
- In Attack on Titan, Annie (usually very stoic) gives off an unsettling laugh and pulls an extremely creepy smile when Mikasa correctly accuses her of being the Female Titan.
- Ren Kouen in Magi: The Labyrinth of Magic laughs out loud for the first time in-story (and apparently in living memory). His subordinates are quite shocked.
- The intro to Paranoia Agent features the cast laughing while in clearly dangerous or unpleasant situations. These include Tsukiko standing on top of a skyscraper holding her shoes, Yuichi and Shogo standing in the flooded ruins of a neighborhood as a monsoon hits them, and Maniwa falling from the sky headfirst.
- Batman in All-Star Batman & Robin, the Boy Wonder was laughing like a maniac while driving through a bunch of cops.
- Perennial Batman villain the Joker is pretty much made of this trope, at least when he's winning or thinks he is.
- The Creeper acts like this, but in a subversion, it is an act. He does it because he knows how disturbing it is to his opponents.
- Baby Face Nelson in Public Enemies, has to be dragged into the car to stop him laughing and killing people. Earlier, in the robbery in question, he is seen cackling "I GOT ONE!" after gunning down a motorcycle cop. The Real Life Baby Face Nelson almost certainly suffered from bipolar disorder (manic depression). And an incident similar to the one seen in the film occurred when the combined Dillinger / Nelson gang robbed the First National Bank in Mason City, Iowa on March 13, 1934.
- A character in O Brother, Where Art Thou? laughs while firing a tommygun. He stops laughing when someone calls him 'Baby Face'. The character is of course Baby Face Nelson. Later after gleefully and manaically robbing a bank, he becomes depressed and wanders off, trailing sad dollar bills behind him. He also laughs and shouts with glee as an angry mob drags him off to the electric chair.
- In Fight Club Tyler Durden laughs like a maniac while Lou beats the snot out of him.
- In the film adaptation of The Two Towers, Gandalf laughs heartily during his Big Damn Heroes moment as he casually beats the terrified Uruk-Hai with his staff. It was glorious.
- A notable trait of The Joker in The Dark Knight. During the famous interrogation scene, Batman keeps punching the Joker harder and harder until the Joker just starts laughing hysterically. The same thing happens later when Batman throws him off a building. The Joker laughs like a Disney villain. (Won't die like one, though.)
Joker: You have nothing. Nothing to threaten me with. Nothing to do with all your strength.
- The Room: Mark tells his best friend Johnny a story about a girl he once knew.
Mark: She had a dozen guys. One of them found out about it; beat her up so bad, she ended up in a hospital on Guerrero Street.Johnny: Ha ha ha. What a story, Mark.
- The Caped Madman from J-Men Forever. He's actually a Gag Dubbed Captain Marvel, so this parodies the Moral Dissonance of those Film Serial superheroes.
- Thanks to the constant abuse of Stock Footage, the opening of Titanic: The Legend Goes On involves two old women smiling and laughing on a lifeboat while the Titanic is violently breaking apart.
- In Evil Dead (2013), Eric breaks into mirthless laughter after Natalie's gruesome death.
- Mike Hammer was this way during World War II, as related in One Lonely Night.
"You should have seen the way they looked at me; you'd have thought I'd had fangs."
- In the Harry Potter series, Sirius Black does this all the time. Notably, when the wizard police find him in a street full of corpses, and later on when he's being killed.
- In Mostly Harmless, Ford Prefect laughs while the earth is being ripped to shreds for the last time.
- In The Belgariad, Mandorallen begins to suffer from phobophobia after he experiences fear for the first time. He's advised that it's normal for brave men to be frightened once in a while, and that he should laugh at his fear to alleviate it. He takes this literally, and makes a habit of laughing out loud while charging into combat, which irritates his companions considerably.
- The Dresden Files:
- Harry's psycho fairy godmother, Lea, likes killing. Really, really likes it.
- Sanya is described as laughing while in combat, though in his case it may be more of an adrenaline issue than Lea's bloodlust. Or maybe he just really likes smiting evil.
- Ganner Rhysode, a wayward Jedi in the New Jedi Order series, struggled his entire life with his need to be the hero. After being captured by the Yuuzhan Vong and rescued by Jacen Solo, he realizes that playing the hero had always been his greatest weakness, but it could also be his greatest strength. He uses the knowledge of who he truly is to become one with the Force and rushes out to hold off the Yuuzhan Vong warriors, buying Jacen the time he needs to enact his plan. After his badass one-liner of "None shall pass," Ganner fights and slaughters hordes of Vong warriors...laughing delightedly the whole time.
- Willy Wonka sometimes does this in Charlie and the Chocolate Factory; Augustus Gloop's mother is horrified that he's laughing hysterically after Augustus has been carried off to who-knows-where via the pipes, and on the boat ride to the Inventing Room, as it speeds off into a dark tunnel, he's "hooting with laughter" as he explains that "there's no knowing where they're going!"
- In The Disaster Artist, Greg Sestero (Mark) wrote that the crew was always deeply disturbed by Tommy Wiseau's (Johnny) laughing, but when he was asked to sound more serious, Wiseau instead read the line in Creepy Monotone, making the crew even more uncomfortable.
- Watership Down. Rabbits have no concept of laughter, so when Cowslip starts laughing, the rabbit protagonists freak out as they can't understand what's happening. Cowslip's warren turns out to be a Town with a Dark Secret, so that's only one of the strange things about the inhabitants.
- Whenever the partners Bruno Wolters and Gereon Rath get into a physical fight (which happens repeatedly) in Babylon Berlin, it usually ends with Bruno breaking into chuckles. By the end of Season 2, it has veered off into downright Giggling Villain territory.
- Guido Geller from Caméra Café is known for his downright moronic laughter (hee-hee), usually when he talks about either old oriental legends, firing someone, or the smell of a fried hamster.
- Adam Adamant Lives!: The usually straightlaced Adam Adamant tends to chuckle maniacally when fighting mooks, especially if he's been played in the episode; needless to say, it really creeps his opponents out.
- The Sherlock version of Sherlock Holmes isn't one for laughter, but you don't see him happier than when he's on a case.
John Watson: Enjoying yourself? ... I'd drop the smile. Kidnapped kids, remember?
- Breaking Bad: The episode Crawl Space ends with Walt lying on the floor laughing hysterically when he finds out that Skylar gave away the money he needed to to buy new identities for the family, right after Gus Fring had declared his entire family fair game.
- Fisk, XO of the Pegasus in Battlestar Galactica, has a disturbing laugh that he gives after relating how Admiral Cain executed his predecessor. Fisk gives another such outburst in "Resurrection Ship", earning himself a puzzled look from everyone in CIC, who are unaware that Cain had just cancelled her orders to terminate them all.
- Buffy the Vampire Slayer:
Sorry, I just got back the memory of seeing King Ralph.
- In "Prophecy Girl" Buffy has a mild episode of very unsettling laughter after she overhears Giles talking about her upcoming prophesied death.
- "Tabula Rasa" has a spell giving the gang, when they're at a depressing point, a mass memory loss where they're engaged in a freewheeling adventure. When the spell is broken they revert to their gloomy selves, then Xander starts laughing.
- In Series 4 of Game of Thrones, Sandor Clegane and Arya Stark arrive at the Eyrie after traveling across the war-ravaged Riverlands and seeing the massacre of Robb Stark and his army just as Arya was about to be returned to her family, only to be told that the aunt Sandor hoped to ransom her to has also died only three days before. Arya's response is to break down in peals of laughter as everyone stares at her in disbelief.
- The House two-parter "Euphoria" starts out with a patient who laughs uncontrollably despite taking a bullet fragment to the skull. It's the first symptom of a contagious disease that soon spreads to Dr. Foreman, who starts laughing while the first patient is bleeding and going into tachycardia.
- In Ajax, the protracted torture of sheep is upsetting enough for Ajax's friends and family, but the sheer glee Ajax derives in doing so (thinking he is torturing Odysseus) just makes it worse.
- In Les Misérables, it's common to have Thenardier let off some cackles during the "Dog Eats Dog" number. Considering that he's gleefully looting the bodies of murdered men, and singing about how the world is a sack of crap, he definitely counts.
- In Porgy and Bess, one of the manipulative Sportin' Life's establishing moments occurs when he spends an entire funeral laughing hysterically, much to the disgust of the others in attendance.
- Deconstructed with Laughing Octopus in Metal Gear Solid 4. True, she cackles madly during her battle with Snake, but it is revealed that she was captured by enemy soldiers and forced to laugh as she killed people. This drove her insane, and it is implied that she continues laughing to keep from screaming or crying.
- In Condemned 2: Bloodshot, the boss character of the Doll Factory tends to get giggle fits related to this.
- Space Channel 5 Part 2 has Purge. It doesn't help that in the Japanese version of the game, he's mentally ill to the point of being a Psychopathic Manchild along with being a Dark Messiah.
- Many, many NPCs in Dark Souls laugh mirthlessly after almost every conversation. It probably has to do with the fact that they are slowly going insane and they know it, and deal with their plight with pitch black sense of humour.
- Team Fortress 2.
- The Pyro. In the "Meet the Pyro" video everybody sees him doing a Menacing Stroll while on a murder spree; then we get to see his point of view: He sees himself joyfully skipping in a Sugar Bowl world laughing and playing with cherubs.
- Also done in "Crackpot", a video for the Saxxy Awards. In the video the Pyro goes killing and mutilating everybody while he believes to be bathing cherubs in a pot (the "cherubs" are body parts).
- Ace Attorney has several Villainous Breakdowns that involve laughter.
- In Damon Gant's breakdown he laughs loudly while clapping.
- Luke Atmey laughs madly when he is caught, followed by a short speech.
- Although it is not seen on screen it was mentioned that Kristoph Gavin laughed after his breakdown.
- Jagermonsters, of Girl Genius fame, tend to go into battle with a joyful demeanour. Then again, they're just so damn goofy that it's hard to think of them as creepy or frightening.
- Lackadaisy's Freckle does this whenever he gets ahold of a gun. He enjoys shooting people perhaps a bit too much. This is actually why he was rejected from the police.
- Bittersweet Candy Bowl has this periodically, most notably from Lucy when Mike throws himself off a cliff to save her, tumbling into the river below in the process.
- A frickin' disturbing example◊ comes courtesy of Red from Ruby Quest during this scene. He has just pulled down the tarp in the room Ruby woke up in the second time, revealing a stitched-up, bloody body pinned to the wall.
- Veronica Carter is always doing this. During the final battle, when she was singlehandedly dueling Valentine in the middle of an Anyone Can Die final battle. She was laughing like a child at an amusement park.
- In If the Emperor Had a Text-to-Speech Device, part of Lucius' Nightmare Fuel factor is his laughter when killing. Seriously, he sounds like deranged version of Mickey Mouse while screaming things like We are all going to skullfuck your families!
- SF Debris has Parody Janeway. Her favourite comedian? Franz Kafka.
- Blitzwing in his Random persona of Transformers Animated will laugh at everything no matter what, but he is especially giggly in battle.
- In Happy Tree Friends, Nutty laughs all the time. Sometimes he even laughs as he dies.
- Popeye and Brutus laugh while they beat the hell out of each other in the 1961 cartoon "It Hurts Only When They Laugh."
- In "Nurse To Meet You" (1945), Popeye is laughing while Bluto beats the hell out of him. That's because all the while the two have been deliberately trying to get hurt so they can be close to nurse Olive Oyl at a hospital, and as a last resort, Popeye force-fed his spinach to Bluto.
- In the Ren and Stimpy episode "Powdered Toastman" after saving the Pope, Powdered Toastman beats up Muddy Mudskipper and ties him to the gun powder keg he had tied the Pope to. Right as the keg is about to explode Muddy laughs like a maniac.
- Robin from Young Justice has the strange habit of doing this.
- At Lizzie Borden's double-murder trial, one of the pieces of evidence against her was the maid testifying that, during the interval between Lizzie's stepmother being killed and Lizzie's father coming home and being killed, she had heard Lizzie laughing at the top of a staircase, and a person standing at the top of the staircase would have been able to see into the second floor room and look at the step-mother's body.
- Tennessee Williams, no tower of strength when it came to Adaptation Decay (in a toss-up, Elia Kazan chose lightning-charged energy over subtlety every time), got his revenge when the film of A Streetcar Named Desire came out. While the rest of the audience would be barking like seals at Blanche Dubois being committed, Williams was wooping it up in the back row. "Now she's off to the bughouse!"