Subverted in Mushishi. When a village and their resident mushishi finally decide to burn a parasitic plant mushi, but after doing so discover that the mushi intentionally takes over like kudzu in order to be burned so the mushi can enter its even more dangerous adult form. After some time spent contemplating the results, Ginko eventually determines that the better option is to hoist it by its own petard, using the adult form to kill the plant form.
In Berserk, when Guts is attacked by several small fairy demons during the Rosine arc, he kills them by leaping into the fire he recently started. Guts is like that.
Schierke, during the battle in the city against the Kushan demon soldiers, proceeds to incinerate a whole bunch of them by summoning a giant fire wheel to set them ablaze.
Farnese's role as the figurehead of the Holy Iron Chain Knights is to investigate reported miracles for the Holy See... which directly translates to "burning people who don't believe or don't believe enough in the Holy See's religion at the stake." And getting off on it. Plus, her history with pets and servants that didn't please her.
In King of Thorn, some particularly tough octopus-like monsters prove vulnerable to good old-fashioned incineration.
Likewise, this is how Alice deals with the Medusa virus when it takes the form of Laloo. However, the smoke from the fire is what likely caused the virus to spread.
In one of his... less stable moments, Izaya sets his whole game board on fire in Durarara!!. Also, Walker sets the Blue Squares leader's van on fire with molotovs when he and the rest of the gang rescue Saki.
And in volume 8 Mikado ends up setting someone on fire. On purpose.
Fullmetal Alchemist: There is a reason why Roy Mustang is known as the Flame Alchemist. One of his most triumphant fights is with Lust. Roy is mostly useless when water is used against him; however, using Havoc's lighter and the oxygen in the water, he was able to create a devastating fire attack that took her by surprise. Then there is the end-fight that is a huge CMOA for Roy; he seared his wound to stop bleeding to death, carved a transmutation circle directly upon his hand, and with a lighter, incinerated Lust multiple times until she finally died.
After acquiring the Legendary Orb of Fire from Mount Aso, Yaiba's answer to any threat becomes "Toss a Giant Fireball at them".
For anyone who wants to put Tomie away for good, this method IS the solution.
In the Excel♥Saga manga, Hyatt catches on fire, horrifying Excel and Elgala and leaving them wondering if burning could cause her Final Death. It doesn't kill her, but her incinerated skin just flakes off, revealing a pristine Hyatt beneath it.
In Nausicaä of the Valley of the Wind, the people of the Valley of the Wind force their conquerors to give them flamethrowers so they can expunge an invasive outcrop of poisonous spores. Then, they turn around and use them to drive out their conquerers.
The Uchiha Clan are reknowned for their fire-based jutsus. Then there is Uchiha Madara himself. He can create Katons so wide and powerful they require dozens of Alliance Suiton users to dispel, or Mei Terumi the Mizukage to counter.
As are Jiraiya and Hiruzen Sarutobi, both have extremely powerful Katon (Fire Release) jutsus. One that Jiraiya created, with the help of Gamabunta was so large it filled in the entire valley that they were fighting in, and one that Hiruzen created needed the Second Hokage, Tobirama Senju to extinguish. In Sage Mode Jiraiya's Katons, now regularly empowered by oil become so strong he can reduce a target to ash with Senpo: Goemon (with the help of Fukasaku and Shima), which sends a wave of fiery oil at the target.
Last not least, the black fire, Amaterasu, that Itachi and Sasuke use, bursts forth at the focus of the user sight and can never be extinguished, untill the thing it targets is incinerated... even if the target is fire itself.
Go ahead, guess what is the main character's superpower in Flame of Recca.
In Bleach, Yamamoto's zanpakuto Ryujin Hakka has powers over fire. As for killing people with it, he does that to Driscoll first, and later he does the same to As Nodt, Busby, and Nanana. And previously, he almost did it to Harribel's girls... but he decided to let them off with a toasting.
An exceptional execution method in Soul Society is taking the criminal to a special hill, restrain them in a Crucified Hero Shot and get them Impaled with Extreme Prejudice with the Sokyouku, a massive halberd that transforms into a flaming firebird when it takes its full form (known as the Kikoo) and pierces the victim, vaporizing their soul. It's reserved only for criminals of the captain rank, and only for special crimes. Aizen had to kill the entire Central 46 and fake commands from them to get the rankless soldier Rukia Kuchiki to be sentenced to execution via that method in the Soul Society arc; otherwise it would never have been possible to use the halberd on her at all.
In Rurouni Kenshin, the government grew wary of Makoto Shishio because he knew too much about their seedier operations since he was Kenshin's replacement as Manslayer. Unlike Kenshin, Shishio was also ambitious enough to use that knowledge against the government while Kenshin became a Technical Pacifist wandering atoner. They tried to preempt a coup by dousing Shishio in oil and set him on fire. Shishio survived though his entire body was covered in horrible burns. Years later, he does attempt to overthrow the government. Though the initial attempt to burn him to death failed, the permanent damage done to his body ultimately does kill him during his final battle with Kenshin.
Deadcoders Reviews's interpretation of XANA took this Up to Eleven: "AHH! KILL IT! KILL IT WITH FIRE! actually, SCREW FIRE, KILL IT WITH FIRE, ORBITAL BOMBARDMENT, DEATH LASERS, CAPTAIN JANEWAY'S CYBERNETIC SPIDERS, ARMIES OF ROBOTS, THE POWER OF STEPHEN KING NOVELS, WEATHER, ELECTRIC TAR, AND ANYTHING ELSE THAT COMES TO MIND!"
In Magic: The Gathering, this is the classic endgame strategy of mono-red: when the opponent builds an army and all other colors' offenses would stall, the red mage points a spell at the opponent's face and torches him to death directly.
In the game's infancy, Red's strategy was Kill it with Lightning.
Mid-game, it's also helpful to wipe out an opponent's creatures with cards like Incinerate, Fireball, and Inferno.
Then there's the character of Jaya Ballard, who's this trope. She's appeared on the flavor texts of over a dozen red spells, including Incinerate and Inferno, and her own card pays homage to these spells.
"Some people have said there's no subtlety to destruction. You know what? They're dead."
"Of course you should fight fire with fire. You should fight everythingwith fire."
"Yes, I think 'toast' is an appropriate description."
Chandra Nalar seems to be the new Jaya Ballard.
Chandra was even taught by Jaya that, "When in doubt, use the biggest fire spell you know." Given that her ultimateabilities are some of the biggest explosions ever seen in red, she's learned quite well.
And like Ms. Ballard, she has a few good one-liners of her own on the subject:
"Who'd want to ignite things one at a time?" "Spontaneous combustion is a myth. If you burst into flame, someone wanted you to."
Sarkhan Vol fights fire with dragonfire.
"Burn" techniques are a good way of reducing your opponent's LP to cinders in Yu-Gi-Oh!. You should be able to guess which Attribute has all of the best burners (hint: it's red and has the Kanji for fire on it).
For a long time in Pokémon TCG, Charizard was the most powerful and valuable card. It destroyed almost every opponent in one hit and had the most HP ever seen. Unfortunately, the ability is quite expensive leading you to "burn away" your deck, though some strategies center around this.
Aside from sonic weapons, fire is the only other weapon generally effective against the symbiotes that give Spider-Man such a hard time.
In Mike Mignola's Hellboy and B.P.R.D. comics, it seems like every encounter with the Lovecraftian underlings of the Ogdru Jahad ends with pyrokinetic Liz Sherman burning the Thing(s) to cinders. Subverted in the most recent case, as it's been revealed that burning Katha Hem to dust didn't quite put him to rest.
This backfires in spectacular fashion in Fables. When Fabletown is attacked by a horde of wooden puppet-men, they have the battlefield strafed with a bit of dragonfire. When Pinocchio sees this, he desperately tries to point out that they're made out of hardwood, and that while they will burn and die eventually in the meantime they've now got an army of nigh-unkillable flaming puppet men to deal with.
Willy Pete. The terrifying, near-invincible Knight of Cerebus from Empowered kills anything that gets near him with fire, as he's a "goddamn fire elemental" whose body burns hotter than the surface of the sun and who's been shown to produce a mind-bogglingly massive amount of flame. Those who aren't afraid of him tend not to learn that they should be until it's far, far too late.
In "The Resurrection of Papa Voudou", the zombiefied Papa Voudou cannot be harmed by bullets or melee attacks, so Vampirella kills him again with the fire on a brazier.
In "She who Waits" the Cobra Queen is killed when Pendragon uses his brandy as fuel for a fire.
In the Godzilla (2014) tie-in comic Godzilla: Awakening, the only way to kill Shinomura is to destroy each and every cell, the most effective way? Burn it. The nuke that was used on Godzilla in 1954 was also used to kill what was left of it.
Better Angels has Shane Walsh emulating Rick's actions during the Zerg Rush at Hershel's farm by setting the barn on fire, roasting the Walkers trapped inside.
Averted in The Immortal Game. During their rematch in the latter half, Celestia attempts to incinerate Terra, but Titan intervenes and prevents it.
Averted again during the second battle of Ponyville; Twilight tries to kill Terra with a concentrated beam of molten iron, but it runs out before she can finish her off.
In A Growing Affection, Naruto wants to make sure an Akatsuki base and its resources are unrecoverable. So he sets it on fire. With a jutsu. That he learned from the Nine-Tails. Without the demon properly explaining how the technique works. He ends up engulfing the base in a roughly one mile diameter circle of napalm.
In System Restore, the second murderer traps their victim in their own cabin and sets it on fire.
In Delenda Est, Harry makes a habit of using Fiendfyre, to the point that Voldemort considers it his trademark.
In thisCrisis Core fanfic/recipe set, we learn that Genesis has some very strong opinions as to what qualifies as "actual" bread:
"In Genesis' universe, square bread is a skin-crawling abomination against nature and must (like many other things) be promptly cleansed with fire."
In the Slender Man ficBy the Fire's Light, it is not the heroes but the Slender Man itself who uses fire to kill things and and cleanse the Earth of things it find abhorrent (which is pretty much everything).
In Home Is Where The Haunt Is, Dipper defeats Mr. Mason this way, by burning down the house, after discovering that Mr. Mason's soul was actually the living house itself.
In Game Of Touhou, House Fujiwara, leaded by Mokou, have this philosophy that enemies must burn. Selenion, Yorihime's pet dragon, can breath fire and uses it to kill everything that crosses his path.
Ferris: This is done repeatedly. Chryssalids have a vulnerability to flame in this universe, just like they do in XCOM Enemy Within.
Subverted in Bungle in the Jungle: A Harry Potter Adventure. Inferiare weak against fire, which means anyone using them to protect something include traps that are activated by fire. According to Bill, flammable gas is the most common. Comes up again in the sequel when Harry points out that Draco's answer of using a fire spell to hold off an inferius doesn't actually defeat it, merely either makes it someone else's problem or causes it to eat you after you exhaust yourself holding it off.
Both applied and subverted in Return of the Living Dead: because the zombies in that movie can't be brought down with simple headshots, the only way to destroy the first one is to incinerate it... but that just causes more problems, because the ashes get into the clouds and the next good rain soaks the land with Trioxin, which carries the virus on. Cue the Zombie Apocalypse! Electricity is shown to do the job later.
Speaking of the first film, Burt Wilson is making last-minute arrangements for the yellow zombie, which he and his employees cut up earlier when Removing the Head or Destroying the Brain doesn't kill it, to be completely obliterated by the oven.
Burt Wilson: You're absolutely certain that this is gonna get rid of everything and do the trick? I mean, nothing left? [Ernie shakes his head] Ernie Kaltenbrunner: Nothing but a little-bitty pile of ashes. Burt Wilson: We don't even want the ashes! [Ernie smiles and leans over the metal grate] Ernie Kaltenbrunner: Then I'll turn it up higher, and we'll burn up the ashes, too. [Ernie slides the zombie into the oven] Ernie Kaltenbrunner: Dust to dust.
Subverted in Evolution; the military plots to destroy the largest sample of the alien entity with tons upon tons of napalm. However, as the scientists find out right as the plan is about to be carried out, fire makes the thing reproduce even faster; a small sample in a petri dish exposed to the flame of a lit match is enough to make it overtake one wall of the room they were in. Instead, the day is saved with dandruff shampooHead & Shoulders.
In Godzilla (2014), Ford kills the MUTO clutch by knocking the valves off a fuel truck, setting them on fire, and running very fast. And, of course, Godzilla's atomic breath, which takes the form of a blue-hot fire stream. Godzilla later force-fed the female MUTO his atomic breath.
In Dawn of the Dead, they burn a group of zombies behind a fence trying to get through by pouring petrol over them. Later they use gas canisters to knock over and kill zombies to get through the masses.
On the DVD extras however, one character says that molotov cocktails don't do anything but make them smell like burnt meat... and make him hungry.
In Live and Let Die, James Bond kills a snake with a makeshift flamethrower, and in Licence to Kill, he sets a villain on fire using a lighter (though said villain was covered in gasoline, so it's plausible).
The giant radioactive ants in the classic monster movie Them! (1954) are hunted through the Los Angeles storm drains by the protagonists armed with flamethrowers.
Office Space. Either averted or played straight, depending on how much of an unholy abomination you consider the office building to be.
In Outbreak, this is the government response to a local outbreak of a deadly virus. (More specifically, using the fire caused by a fuel-air bomb to starve the place of oxygen. No oxygen, no hosts; no hosts, no virus.)
In Westworld, Richard Benjamin's character attempts to do this to the Yul Brenner Gunslinger robot. Doesn't quite work, though.
In Outlander, the Moorwens were driven to the brink of extinction by the firebombing of their homeworld. Kainan replicates this in ancient Norway, by luring the solitary Moorwen into a pit filled with whale oil and lighting it on fire. It only succeeds in singeing and ticking off the creature.
Subverted in Child's Play, where the protagonists burn devil doll Chucky to a crisp. It only makes him angrier and freakier-looking.
Subverted in The Terminator, when destroying the titular indestructible death-robot's gasoline truck seems to work for a little bit, but his creepy-ass metal endoskeleton just gets up again after a few seconds, despite the fact that all its skin just got burned off. When fire just isn't hot enough, you can always try molten iron, as in the 2nd film.
In The Crawling Eye, the titular alien creatures are destroyed when the Air Force napalms the mountainside where they had gathered. Whether such techniques were necessary aren't really known, though, since it was the first thing the humans had tried.
The Elite Squad has the drug dealers using a Truth in Television technique known as "microwave" - the victim is put inside a pile of tires, which are then set on fire (during the shooting of that scene, the criminal "consultants" had to remind the ones being burned to scream horribly).
This was the original solution to the Freddy Krueger problem in A Nightmare on Elm Street. Partially subverted, considering he just came back as a dream demon with horrible burn scars.
What ultimately happens (probably by accident) to the Third Castle in Ran, preventing Lord Hidetora's seppuku by driving him insane. Well, that and the broken sword.
In most zombie films, only a headshot will terminate the walking dead. In The Living Dead at Manchester Morgue, also known as Let Sleeping Corpses Lie, zombies are primarily killed with fire. And they go up pretty easy.
The final airstrike in Platoon, in response to a request by The Captain to "expend all remaining ordnance on my pos", includes plenty of napalm mixed in with regular bombs. The firestorm almost obliterates everything and everyone left.
In Apocalypse Now, Kilgore leads his men into battle in a formation of helicopters in order to storm a beach with "Ride of the Valkyries" playing to intimidate the enemy, all so that they could surf on the beach for that day. Naturally the Vietnamese suffer plenty of fire from the helicopters and the men on the ground but the climax of the battle comes when Colonel Kilgore calls in a massive air strike that obliterates the opposition. As Kilgore watches this he famously expresses how much he loves to kill things with fire, even going so far as to reminisce about a massive air strike he witnessed during an earlier battle during the Vietnam War where he marveled at all the destruction that the bombs caused, remarking to Captain Willard and Private Lance:
Colonel Kilgore:You smell that?
Kilgore:Napalm son. Nothing else in the world smells like that.I love the smell of napalm in the morning.You know one time we had a hill bombed for 12 hours and when it was all over I walked up. We didn't find one of 'em, not one stinking dink body. The smell... you know that gasoline smell. The whole hill. It smelled like... (sniffs the air, pondering for a moment) victory. (Mortar strike goes off behind him, Colonel Kilgore doesn't even flinch) Someday this war is gonna end.
In Dagon fire seems to work well on the fish men and their cult.
Completely averted in, "Tomie: Another Face", one of the movie adaptations of the manga, Tomie, where the eponymous Nigh InvulnerableBody Horrorific teenage girl is burned in the incinerator by the Doomed Protagonist. However, her burned ashes gather up and create her face in the air, reminding the protagonist that she will never die and that every single one of her ashes will become a new Tomie.
In Tarantula the only way to destroy the eponymous giant spider is for the Air Force to napalm it.
In the first Blade film, Blade uses fire on one of his enemies. This doesn't kill Quinn (who is a vampire) but it probably makes him wish it had, at least for a while. Funnily enough, Blade probably only set him on fire as a new form of bullying Quinn.
Blade: Quinn, I'm getting a little tired of chopping you up. I thought I might try fire, for a change.
In the climax of Anaconda, they try to kill the largest Anaconda by setting it on fire after it's trapped in a factory pipe. This ends in a bit of Infernal Retaliation as it still goes after them while it's on fire before it slinks away in the water. Even that doesn't kill it, and it takes a pick-axe to the skull for the Anaconda to ultimately die.
In Daniel Handler's A Series of Unfortunate Events: In the Village of Fowl Devotees, burning at the stake is the designated punishment for breaking any of the town's numerous rules (which includes the biggies like murder, but also trivial and ridiculous offenses like using mechanical devices, reading certain books, and talking out of turn in town meetings).
It's not so much a case of panicking as even noticing: flamethrowers are more effective than guns because Triffids don't appear to have any vital organs. (Following the same principle, shotguns work better than handguns or rifles.)
Harry Potter and Dumbledore use it to drive off the Inferi at the end of The Half-Blood Prince. And in Deathly Hallows, Fiendfyre turns out to be one of the few ways to destroy Horcruxes.
Notable for the brilliant exchange between Harry and Dumbledore that went something like...
Dumbledore: However, like many creatures that dwell in cold and darkness, they fear light and warmth, which we shall therefore call to our aid should the need arise. Harry:(bewildered expression) Dumbledore:Fire, Harry. Harry: Oh... right...
J. R. R. Tolkien's The Lord of the Rings—in the first fight against the Ringwraiths, swords prove ineffective, so Aragorn grabs a flaming piece of wood form the fire and drives them back. Works remarkably well considering they are the immortal indestructible specters of long dead kings, capable of killing with even a slight blow and causing even squads of veteran soldiers to run in fear. It's hinted, though, that the Ringwraiths are in a weaker state during their initial attack on the Shire.
Somewhat justified as they are at the point described as being stronger in the dark, and that they need the cloaks to have form and to affect the world. Cloaks can burn and fire is bright light.
Also, in the modern movie adaptation, fire is the orcs' most useful weapon against the Ent attack. Which is a pretty good idea, as Ents are trees. When Isengard is flooded, you can see a burning Ent rush forward and dunk itself to douse the flames.
In the books Saruman uses some kind of automatic flamethrowers against them, causing them to flood Isengard.
In the books, the dwarves' need for firewood (for their forges) was one reason Ents didn't like dwarves very much. There is a bit in The Two Towers where a tree bends down to get some warmth from a fire, but in general, the trees don't like it.
In Scott Westerfeld's Midnighters trilogy, the animals are afraid of human technology, including, but not limited to, fire.
In Terry Pratchett's Discworld, werewolves can only be killed by either silver or fire. Likewise, zombies, vampires and mummies are very flammable.
In The Hobbit, fire proves effective in driving off wargs, but much less so when some goblins arrive, who simply use it against the dwarves.
The Zombie Survival Guide notes that fire is the only way to safely dispose of a Solanium-infected corpse. It's not that effective as a weapon, because the zombies don't feel pain and won't notice they're on fire, but all traces of the infection will be wiped out once the fire brings them down.
And in World War Z, the Army develops an incendiary bullet, nicknamed the "Cherry Pie", designed to burn up a Zombie's brain without causing collateral damage.
And Daenerys, of course, has her three pet dragons. The very first things she trains them to do is breathe fire at people. And she has ambitions to use said dragons, once they grow up, to conquer Westeros. Her family's motto isn't "Fire and Blood" for nothing, after all.
And who could forget the Battle of the Blackwater when Tyrion Lannister packs a squadron of ships with wildfire (which is basically magical napalm on steroids) and sets not only both fleets but the river itself on fire.
As in Mythology above, the vampires in numerous works of Gothic literature—including Carmilla, Varney the Vampire, and Dracula must be destroyed with fire after they're staked and decapitated. The fact that Dracula's body is not burned when he's killed in the original novel is often cited as a reason for latter-day authors to bring him Back from the Dead. Again.
A subversion: in H.P. Lovecraft's The Case Of Charles Dexter Ward, a repeated theme and instruction is to refrain from killing the necromancer villain with fire, as he can be resurrected from the ashes. Instead, the protagonist is instructed to dissolve the body in acid.
It's worth noting that Carlisle failed to try immolation during his many attempts at killing himself after he became a vampire, despite his father being a pastor who believed in wiping out evil supernatural creatures in such a manner.
At the end of the Jurassic Park book, there isn't any of that "Let the dinos live in peace on the island" stuff from the movie. The Costa Rican Air Force levels the island with napalm.
In Brian Caswell's The View From Ararat, the only known ways to destroy the inorganic super-plague threatening life on planet Deucalion are extreme heat, and an enzyme conveniently found in all native Deucalion plants and animals, half a galaxy away from where the disease first surfaced.
The finale of Peter F. Hamilton's Night's Dawn trilogy, The Naked God, has a straight example—the Orgathe are immune to most weapons but very vulnerable to heat.
In Dan Abnett's Warhammer 40,000 novel Brothers of the Snake, when Khiron killed a fellow Space Marine, he claimed he had been possessed by a daemon and that, since he had not used fire, it had escaped. Fortunately, Priad remembers this when he figures out who it escaped to.
1408 is an inversion: the protagonist sets himself on fire to shock himself back to reality and escape the room. It works.
Subverted in The Road Virus Goes North, a short story by Stephen King. A horror writer buys the last surviving painting of a troubled artist who burned all his other works and then committed suicide. When he realises the painting is cursed he tries to get rid of it, but the painting keeps returning intact. Eventually he burns the picture, because that's what works in the books, right? Unfortunately it turns out that the artist didn't burn all his paintings except this one, he burned all his paintings including this one.
Subverted in John W. Campbell's "Who Goes There?" where the scientists in Antarctica use high voltage electricity to kill telepathic, body-morphing aliens. This makes a lot more sense than the flamethrowers used in the movie (John Carpenter's The Thing (1982)) because it takes a while to kill something with fire. Electricity can zap every cell in an organism instantly—hard to adapt to, eh? For another good reason to use electrons, see the end of the movie, where the entire base is charred rubble and the survivors are shelterless in ANTARCTICA.
Played straight in the conclusion of the original story - the final alien is destroyed with an oversized blowtorch after a human fires bullets through all three of its eyes, which causes it to become immobilised. Also, the electrocution weapon required mains power from the base's generators, and the final confrontation is too far away to run a lead.
In P.C. Hodgell's Chronicles of the Kencyrath, fire is the best way to kill the shapeshifting, vampiric Changers, which are hard to kill but whose blood is very flammable. It's also the best way to kill the zombielike Haunts.
In the Night World series, fire is the only thing that can kill any creature, be it witch, human, werewolf, shapeshifter, or vampire. One character does freak out when another speaks nonchalantly about burning a werewolf to death (including the phrase "one of the traditional methods"), so it appears to be a less-used tactic... now.
A tanker truck, a fire truck, and an intentionally damaged bridge that the Posleen have to cross provides much fun for the humans defending Fredricksburg, at one point in Gust Front.
Sun Tzu devotes a chapter of The Art of War to the use of fire against an enemy.
When Harry Dresden of The Dresden Files yells "Fuego!", you take cover and pray for mercy. When he yells "Pyrofuego", you run for your damn life. He's only had to cast the latter spell twice in the entire series, and both times, those on the receiving end... let's just say they had their whole day ruined. Memetic Mutation has turned him into the Anthropomorphic Personification of this Trope.
Don't forget, one of those times he was so furious that he said "Pyrofuego! BURN!" Meaning he may have cast the spell in English. Something that is pointed out many, many times to be terrifyingly dangerous.
His very first duel involved an Eldritch Abomination, a gas station, and fire. Harry won. (Note, though, that Harry eventually discovers the Eldritch Abomination threw the fight, and it could've ripped him apart easily.)
He's also a fan of a shotgun loaded with fireball or dragon's breath rounds, as is Kincaid.
Harry also once created a spear of flame 20 stories high. Not for nothing does Elaine (no slouch herself) refer to him as the most powerful wizard she's ever met.
A bit of clarification: In terms of raw power, Harry is in the top percentile. However, Harry himself notes that more experienced wizards, such as the Wardens or the Senior Council could twist him into knots without even trying, because in the Dresdenverse, skill matters much more than power.
This one was neat because he wasn't even using it as a weapon - the fire was a heatsink for a lake. Magic is such a Game Breaker that it's not even funny. note It's hilarious.
"How about a little fire, Scarecrow?"
The Holy Fire of the Swords (and occasionally their wielders) is very effective against the forces of darkness.
Harry: Let that be a lesson to you. Hands off the Fist of God.
Don't forget the use of superpower hellfire and soulfire.
Don't kill kids near Harry. He will set the fat inside your body on fire.
In-universe, Harry notes that fire really is a highly-effective weapon against all sorts of nasties, as well as being used against magical enchantments. Fire can disrupt and destroy enchantments when used with that intent, and any wizard worth their salt in combat learns how to use fire first. In Turn Coat, a squadron of Wardens cuts loose on a horde of summoned spirits, and the ensuing literal firestorm is simply stunning to behold.
Although all the Elemental Powers in Codex Alera are useful in war, using firecrafting to make a Flaming Sword is a common tactic when High Lords are fighting because wounds that have been cauterized are extremely difficult for watercrafters to heal. Fire is also handy against the Vord, since the croach they rely on to keep them alive is very flammable.
The beam of sunlight (while technically a product of aircrafting) is a prime example.
In the conclusion to An Enquiry Concerning Human Understanding, Scottish philosopher David Hume says that reasoning can only lead us either to mathematical truths or knowledge about matters of fact based on experiment:
If we take in our hand any volume; of divinity or school metaphysics, for instance; let us ask, Does it contain any abstract reasoning concerning quantity of number? No. Does it contain any experimental reasoning concerning matter of fact and existence? No. Commit it then to the flames: For it can contain nothing but sophistry and illusion.
As mentioned in the main description, the trolls in the Forgotten Realms world regenerate and can recover from anything...except being set on fire. The heroes in Streams of Silver take advantage of this weakness as much as they can.
The Krytos Plague in the X-Wing Series is so highly infectious that decontamination of a building consists of burning everything inside it with plasma, including burning half an inch of concrete off the walls.
In the last Time Scout book, a bad guy running from the heroes tosses a burning rag onto a barrel of gunpowder in the middle of an arsenal in the middle of Victorian London's dockland. This causes some commotion.
In Michael Moorcock's The Sailor on the Seas of Fate there's a scene where the heroes have to destroy a pair of buildings. The captain of their ship is insistent that the buildings can only be destroyed by fire. It turns out that the buildings are a pair of evil alien sorcerers.
In H. G. Wells's short story "The Cone" an angry steel worker decides to kill his boss by throwing him off of an overhead catwalk onto the red-hot vent cone on top of a blast furnace. His victim starts burning immediately, and it goes From Bad to Worse when the vent opens releasing scalding gases.
The only reliable way to kill the undead in The Witch Watch. That and just cutting their heads off and leaving it powerless and buried underground whilst still being conscious.
Kantri of Tales of Kolmar have this instinct towards anything that makes them angry. They use claws and teeth too and will rend bodies long after the foes are dead, but when it's over they burn the bodies and preferably things the bodies have touched, right down to the soil. They aredragons.
In The Bible, after discovering there's only a single righteous resident at the cities of Sodom and Gomorrah (it was Lot, the nephew of Abraham), God (through two of his angels) told Lot to leave the city. After Lot did what he was told, taking his family to escape, God did exactly what this trope says — a rain of hellfire and brimstone reduced both cities to ashes.
He did something different in Egypt, where He used burning hail — in other words, ice that is on fire.
Aaron's sons Nadab and Abihu burn incense in a censer when God hadn't told them to. "So fire went out from the Lord and devoured them, and they died before the Lord."
This seemed to be Elijah's M.O. Just ask those soldiers.
Nebuchadnezzar's preferred method of execution in the book of Daniel.
There is Hell if you want your gratuitous fire usage. While Hell became more associated with fire after Dante wrote The Divine Comedy there are a few associations between fire and Hell in The Bible itself.
In Judges 18 the Danites while looking for land massacred the people of Laish and "...burned the city with fire."
Under Mosaic law, fire was the standard, final "treatment" for garments or buildings that had been infected with disease/mold/etc. First, you were supposed to try water. If that worked, great. If it didn't, burn it.
In Septimus Heap - Physik, Queen Etheldredda's ghost and her pet animal are finished off by burning their portrait in an appropriately designed BoneFyre.
In The Wheel of Time series, fire is one of the three weapons effective against the Finn. Music puts them in a kind of trance, and while they can become intangible, pure iron and fire will still hurt them. The explanatory poem goes:
The Vampire Chronicles, like many other vampire stories (as noted above) have fire as one of the only ways to destroy a vampire note Though particularly strong/old vampires are immune even to that.. Louis de Pointe du Lac, narrator of the first book, has a particular fascination with it, burning down two houses, a theatre, and his creator within his book alone.
A peculiar variant with the fire-spiders in The Quest of the Unaligned. Their own natural pyromancy means that fire doesn't actually hurt them, but exposure to a lot of fire affects them like Alien Catnip. This more-or-less saves the heroes' lives when one of them accidentally fills the cave they're in with an inferno and stuns the vast swarm of fire-spiders for over a hour, allowing the heroes to escape.
The Enemy employs this against the Zombies several times, it seems to be the most effective weapon against them, unfortunately it's the hardest to safely employ.
Most Secret by Nevil Shute is about a fishing boat during World War II that is fitted out with a large flamethrower in a plan to destroy the German escort vessels keeping an eye on the French fishing fleet. The Kill It with Fire trope is specifically lampshaded.
Live Action TV
In Supernatural, "salt and burn the body" is the standard solution to malevolent spirits and such. If the body's already been cremated, the boys need to find an alternate solution. Sometimes this means finding the little bit of the body that wasn't burned and setting fire to it.
Also, in the episode "Metamorphosis", this is the only way to kill of a Rugaru.
Then there was the time Angel became the Big Bad, killed Jenny, then set up the body to get off on how the heroes would react to her murder. That was too much for a distraught Giles, and the former Ripper loaded up with a bowgun, fuel bombs and a freaking flaming baseball bat.
In Season 8, Renee lures a vampire before Buffy attacks it, then flicks a lighter and gives a Psychotic Smirk as Willow douses him in petroleum. After Buffy interrogates him he pleads for his life, saying he answered her questions, she has to let him go.
I never promised that.
In Season 9, Angel and Faith fight demons who can regenerate, so they use a flamethrower to burn their whole bodies into ash.
On one episode, Wes and Fred went after a demon nest with blowtorches, setting the whole thing ablaze.
Sometimes however vampires can put themselves out before being incinerated.
Averted when Wesley burns Lilah Morgan's employee contract which binds her to Wolfram & Hart for eternity. A duplicate contract immediately appears in the drawer.
Not necessarily fire, but Sebaceans on Farscape go into horrendous unrecoverable comas if their body temperature gets too high (and at levels that would be on the high end of tolerable for most other races, too), making deserts, low fevers, and oversized bonfires potentially deadly. Given just how badass Aeryn is when not suffering heat delirium, it might count.
Scarrans, who have the power to project their body heat into deadly beams, love using this against their enemies- especially Sebaceans.
Ditto the fire-breathing Sheeyangs.
On LOST, Kate burned her drunk & abusive father (and his whole house) to the ground.
In the season five finale, the Man in Black kicks a dying Jacob into a firepit to finish him off.
And then there's The Others in 1954 who use a storm of flaming arrows to kill off a large number of 815 survivors
A recent episode of Stargate Universe has them using flamethrowers to hold back a very aggressive alien parasite that seems to creep along the ground like a fungus. How flamethrowers got aboard Destiny is anyone's guess. Greer states that he made them in his spare time, thinking they might come in useful.
In the series Legend of the Seeker (as well as it's book counterpart), the only way to permanently kill a baneling is to burn the body so it cannot be revived. A method the resident wizard Zedd uses proficiently.
In The Vampire Diaries, Stefan killed Ben with a freaking flamethrower! Also how they disposed of the incapacitated tomb vampires. Bonnie threatens Damon with this - and nearly goes through with it. Damon tries this with Elijah, but fails.
In The Walking Dead, a flashback shows the army dropping napalm on Atlanta in a (futile) attempt to contain the outbreak.
Ice Cube's "We Had To Tear This Motherfucker Up" is about the L.A. riots. Including the rash of arsons. It's from the point of view of a rioter.
Amon Amarth has numerous songs about the fires and fire god of Ragnarok. "Gods of War Arise" describes vikings burning own a sleeping village.
P!nk has a single - Funhouse - that seems to relate the story of killing Monster Clowns with fire. A perfectly reasonable response, wouldn't you say?
This used to be a funhouse, But now it's full of evil clowns. It's time to start the countdown I'm gonna burn it down, down, down I'm gonna burn it down.
The Prodigy seem to like this trope a lot. Songs include "Fire", "Firestarter", "Fuel My Fire", "Spitfire", "The Heat the Energy" and "World's on Fire". In the same let's-burn-the-world vein you could probably also include songs like "Molotov Bitch" and "Hotride".
In Rammstein's "Rosenrot" video, Till's character is burned at the stake.
And in a later video, Haifisch, when Schneider daydreams about killing Till, this is his method of choice.
Swedish industrial metal band Raubtier: "Lĺt napalmen regna ner!" (Let the napalm rain down!)
Heracles used fire to cauterize the Hydra's stumps before it could grow new heads. Or to be precise: Heracles smashed the heads with his club, his nephew Iolaos cauterized them. This technically didn't KILL the Hydra, since one of its heads was immortal. He just buried it under a rock afterward.
Many of the admittedly extremely varied world folklore about vampires feature either an aversion to fire, or immolating the vampire's remains as the final step in destroying it for good.
In Plants vs. Zombies Pinball, the Torchwood Pea turns your pinball into a fireball, while the Jalapeno sets a lane on fire, burning all the zombies in it.
Dungeons & Dragons has this for trolls (although acid works just as well). Based off the Hercules example, it's necessary to cauterize the hydra's stumps so new heads don't grow. (Save for fire breathing hydras. They need ice.)
Fire is also extremely useful against most undead, who are often immune to a wide variety of attack modes.
In general, when wizards start to cast Fireball is the point where they being to outshine the fighters in combat, and most of the high level, high damage spells tend to be fire.
Apocalypse from the Sky is a ninth-level spell from the Book of Vile Darkness. It isn't too damaging for a ninth-level spell (10d6 to all in the radius, which is available seven levels previously), but it has a radius of ten miles per caster level. The weakest person who can cast this spell would be destroying small countries and almost everything in them, and all of it would be through FIRE.
The psionic version: the Pyrokineticist. Always chaotic, rarely good, invariably fire-heavy. They are so fire-happy that a prestige class prerequisite is "must have set fire to a structure of any size simply to watch it burn"
Searing spell is a feat you can apply to Fire spells to make them ignore Fire resistance, and partially BYPASS FIRE IMMUNITY! It burns so hot it can burn things that can't be burned!
4th edition gives us the Irresistible Flame feat. An epic-tier infernal warlock or pyromancer can simply burn straight through fire resistance. Not as useful as the previous edition's Searing Spell, but still fun.
And Dragon Magazine for the same edition gives us Burn Everything, which does the same thing from heroic tier. Less powerful than Irresistible Flame, but available to any arcanist from first level on.
Early editions of the game had flasks of oil that could be set alight and hurled at monsters, like weak Molotov Cocktails. Now there's flasks of Alchemist's Fire with more or less the same effect. They burst into flame on impact.
In short, Kill It with Fire is a common and undeniably effective method of dealing with problems in DnD and many other tabletop games.
Fire deals aggravated damage (much harder to heal) to every creature in the Old World of Darkness (The primary except is demons). In the new one, fire just deals lethal damage (painful, but not "OW MY VERY BEING IS RENDED" like with aggravated) to mortals and those not vulnerable to it. Vampires and Prometheans receive aggravated damage from it, however (Vampires because they're desiccated corpses held together and made lively by magic, and Prometheans because the "Divine Fire" that gives them life overloads when exposed to fire).
In the Old World of Darkness, the vampires of the Setite clan were especially weak to fire, taking double damage from it (still aggravated). In the new one, their Spiritual Successor, the Mekhet clan, has inherited the weakness.
The Vampire: The Masquerade / Mage: The Ascension crossover supplement "Time of Thin Blood" saw the Technocracy respond to the rising of the Ravnos antediluvian in Bangladesh by declaring Code Ragnarok... and then beating the shit out of the ancient vampire by setting him on fire with orbital mirrors after nuking him from orbit with nukes enhanced by Awakened Science. Up to that point, everything else that various supernatural groups (i.e. Garou werewolves, Asian vampires) had thrown at Ravnos had been ineffective. So, yes, on that day, the much-maligned Technocracy saved the world. Take That, mages.
A vampire can heal lethal damage (swords, etc) at the rate of one Vitae per point. This isn't bad: most vampires can just abduct some random passer-by, drain him dry, and be peachy. It takes three days and only slightly less blood than the average person contains to heal a single point of aggravated damage.
Exalted has the flame piece and firewand, and their First Age brethren liked the plasma tongue repeater. The Righteous Devil and Golden Exhalation martial arts styles let you do things like triple these weapons' (usually limited) range or do bonus damage. Fear the Exalt who masters both of these styles and is able to use a Charm to produce ammunition - especially since the martial arts skills required to reach the higher levels of those charm trees mean that they can still kick your arse if you disarm them.
What, no mention of Fire Aspects? They're an entire caste of Exalts themed around burning their enemies to death!
This is official government policy towards all threats in Warhammer 40,000's Imperium of Man. Aliens? Reduce them to ashes. Mutants? Burn away their impurities. Nonbelievers? "Light your way in the darkness with the pyres of burning heretics." Chaos cults popping up everywhere? Kill the planet with fire. The Imperial Church Militant's troops, the Sisters of Battle, specialize in this in-game, with a significant percentage of their troops being armoured women carrying huge flamethrowers. Sisters of Battle Seraphim can even dual-wield flame throwers.
The other races are pretty prone to this—almost every race has some sort of flamethrower equivalent, such as Ork "Burnaboyz", who combine flamethrower and armour-cutting blowtorch in one device. They generally tend to be constantly working on deconstruction, lest they get bored and make other Boyz "do the burny dance."
See also the Cult of the Red Redemption, in Necromunda. While the Sisters of Battle manage a healthy 0.2-0.8:1 flamethrower-to-soldier ratio in their various squads, virtually all Redemptionists carry a flamethrower, flamethrower pistol, underslung single-shot flamethrower on their rifle, or all of the above. Even their giant chainswords have a flamer built onto them.
The Imperium's military as a whole gives us flamethrower pistols, full-sized flamethrowers, vehicle-mounted flamethrowers, even Humongous Mecha-sized flamethrowers, plasma guns, and the meltagun, which is an anti-tank microwave.
Prior to their 5th Edition Update, the Grey Knights' Incinerator weapon was the idea of this trope taken up to 11; it's blessed flames were so hot that even immaterial forcefields were useless against it. Since Flamer template weapons automatically ignored all cover saves as well, this means that the only thing safe from the Incinerator was extremely tough armor. Good thing it only had an AP value of 4, otherwise even Space Marines would be crying in face of it.
Not to be outdone, the Eldar don't just bring flamethrowers - they bring a weapon that literally creates a wave of flame-like stuff that is actually torn space leading into hell. It rips through even the strongest armor, as Hellfire should, and can even carry those it wounds into hell, never to be seen again. Not so much "Kill it with fire" as "replace the space where it's standing with solar-core-hot fire".
Confronted by Treemen? Fireball. Being attacked by mummies? Burning Gaze. Taking on anything else? Conflagration of Doom. There's one lore of magic that is based entirely around killing it with fire, plus the various versions of the Lore of Tzeentch (which MUTATES it with fire).
There's a category for Breath weapons, and a special rule for Flaming Attacks. They are often combined. Case in point, dragons, and the Salamanders of Lustria, who are living dinosaur flamethrowers.
And then there's the Dwarf and Skaven entries... the Dwarf Flame Cannon and the Skaven Warpfire Thrower. SkavenbeingSkaven, it's rare for the Warpfire Thrower to be used consistently on the enemy.
This is also useful to deal with Skaven Hell Pit Abominations, since killing them with fire inhibits regeneration and prevents them from rolling on the aptly named "Too Horrible to Die" table. Said table can involve them spitting out rat swarms, or standing back up with damage restored and a temper.
Among the many religious or mystical denominations in Fading Suns, the Templar Avesti are the most prone to a Kill It With Fire approach. Their church's symbol is a holy flame. Avestite inquisitors and zealot monks wear fire-retardant robes with breathing masks and carry flame throwers when they do battle with mutated monstrosities.
In Ars Magica this trope sums up Flambeau's magical philosophy (at least prior to 5th edition).
In GURPS: Magic you can create "Essential Flame" which will actually burn water elementals. A pyromaniac mage actually has a lot of fun options, besides the ever popular "Explosive Fireball" there is "Burning Death" which incinerates target from the inside out even if they're magically protected from fire.
Crimson Skies has an aircraft in it called the Blackflag Firestorm. The plane earned that particular name when one of the first prototype fighters' guns were loaded with magnesium rounds and it spread so much fire across the sky that onlookers had thought the air itself had burst into flames.
Call of Cthulhu adventure Terror from the Stars, insert "Field Manual of the Theron Marks Society". The Manual says that you can use an "Indian Water Pump" filled with gasoline as an improvised flamethrower. Just spray the monster with gasoline, then set it on fire.
BattleMechs can be equipped with flamers and inferno missiles. Both of these weapons are designed to damage 'Mechs not by burning them, but rather by overheating them. However, they can quickly and gruesomely annihilate infantry teams and any of the few types of battle armor or vehicle that isn't specifically shielded against fire attacks.
Voldemort in Harry Potter and the Escape from Gringotts sends a living skull-like fireball towards the guests, only for it to be destroyed at the last second by the firey breath of the dragon that the main trio ride on.
Subverted in BIONICLE, in which Tahu defends himself from Nektann by using his fire powers to melt most of his enemy's armour off and incapacitate him- but making a clear point of not killing him in the process.
That's how you deal with trolls, beasts and giants in Stand Still. Stay Silent. First you burn all the land, then you blow up everything still standing, then you leave it to freeze in the winter, and after such treatment, you burn it again, just to make sure. Believe it or not, it's not overkill.
Belkar: It's as true today as when I started adventuring: when in doubt, set something on fire.
And later the Death Knight when fighting Chang's group of soldiers.
Death Knight: "Burn."
In Tales of the Questor, the ratlike Wights swell and explode when exposed to a candle flame... later on, Quentyn uses magically amplified torchflame to kill a swarm of Redcaps (with messy, gory, tick-poppy type results.)
Kyros from Irregular Webcomic!. His obsessiveness to "sort out" any problems he faces by casting a huge fireball, killing everything in his path (usually including himself) is a Running Gag.
From the same author plus a few more, The Rant for thisDarths & Droids strip discusses how fire is the most fun and threatening of the elements.("Seriously, which enemies would cower in their tracks if you appeared in front of them and proclaimed yourself to be a great water wizard?")
Amy said, "So, you're making a flame-thrower?" "Amy, we gotta be prepared. We don't know what we?ll find in that place, but for all we know it could be the devil himself." "David, what possible good is that thing gonna do?" "Oh, no, you didn't hear me. I said it's a flame-thrower." Girls.
MAN COOK MEAT WITH FIRE. Not "man show fire to meat and then eat it while it still squirts and pulses." KILL IT DED WITH FIRE YUS. "Medium rare" = "good vet could get it up on its feet in an hour or two." That's not cooked with fire. That's THREATENED with fire. I do not season steak. Start seasoning steak and before you know it? You're French.
Uncyclopedia refers to fire as "nature's weapon attachment".
In Orion's Arm this is one of the best ways to deal with nanotech attackers. The tiny robots can't shed heat effectively and will rapidly disintegrate when heated.
Happy Tree Friends: Every single character in the series dies in "Class Act" as a result of the fire that burned down the school, including the ordinarily Nigh Invulnerable Flippy, Cro-Marmot, and Splendid.
In the Darkwing Duck episode, Night of the Living Spud, a redneck decides to test how flammable a vampire is.
Seems to be the only way of doing any sort of decent damage to Madam Rouge from Teen Titans. She's damn near invulnerable to any kind of physical attacks.
Avatar: The Last Airbender: Fire Lord Ozai decides this trope is an appropriate response to a recalcitrant Earth Kingdom. Why bother with normal methods of subjugation when you can just set the continent on fire? Azula suggested it.
Scrotus threatens to show Korgoth of Barbaria a new spectrum of pain, and Korgoth responds by tearing a substantial amount of Scrotus's skin off, dousing him with strong alcohol, and lighting him on fire.
A Halloween episode of The Simpsons had Maggie suddenly loses her legs and grows tentacles. They take her to Dr. Hibbert, who prescribes "fire, and lots of it". This is apparently his cure for everything.
In "Bart Carney," a father/son carny team takes over the Simpson house. In trying to think of a way to take back their house, Bart, Lisa, and Homer are each keen on fire as an option - one that Marge keeps vetoing.
Bart: I say we set fire to the house, kill them that way. Marge: We don't want to kill them, we just want our home back! Lisa: Well...if we did set fire to the house.. Marge: No fires! Homer: I've got it! Marge: No fires!
In "Lisa's Sax" when Marge shows Homer a picture an upset Bart drew
Marge: Homer, I want you to look at this drawing Bart did. Homer: [watching TV] Oh, it's beautiful! Oh, oh, let's put Bart's beautiful drawing up on the fridge! Marge: Homer, stop. Will you please look at the drawing? Homer: Oh, all right. What...[looks at drawing]...aaah!! Burn it! Send it to hell!
In one episode, Homer has to take care of an endangered caterpillar. Lisa researches the species and discovers that it is "sexually attracted to fire". Homer concludes that God must want the species to die.
In "Headhunters", Dipper and Mabel defeat the evil wax dummies by melting them, with Mabel throwing some of them in a fire for good measure.
In one segment of the episode "Bottomless Pit!", Dipper has his voice changed to sound much deeper. Soos' first response when hearing it is to beat Dipper with a broom and yell "Kill it! Kill it with fire!"
Long before there was any scientific understanding of germs and other microbes, humans had learned that fire made rotting corpses and things that had been in contact with sick people and animals harmless. If cleaning infectious things with water didn't work, fire would do the job as a last resort, which makes fire the ultimate form of purification in cultures all over the world.
Cooking, another reason for the symbolism of fire as purification: Kill parasites with fire. Suffer not the tapeworms to live. Despite the lack of knowledge concerning parasite infestation, humans learned that cooking was an efficient way to sterilize food and render death from food poisoning less likely. This was a highly important evolutionary step in that, while our immune system is moderately badass at killing single-cellular organisms such as bacteria (if the bacteria does not overwhelm the body first), it is completely useless against multicellular parasites that can steal vital resources, or clog up the digestive system, or eat your organs or brain alive inside out! And before cooking, the alternative to the Paranoia Fuel of raw meat was an inefficient diet of indigestible plant cellulose that require a slow ruminant fermentation complex to manufacture any meaningful amount of proteins and essential fatty acids (e.g. cows and gorillas didn't need fire-creating intelligence, and instead of that, they evolved for microbe-filled appendixes to support their fat-less vegetarian lifestyle, although then can Ascend to Carnivorism anytime). Carnivory evolved as it made resource acquisition fast, and cooking made the resource acquisition from that even faster. The Prometheus parallels also exist in this evolutionary history; a popular theory proposes that it was cooking that allowed us to eat fat foods with impunity and extract energy from food more efficiently, which provided enough fuel to develop our fat-ass energy-hungry brains which allowed us to think of more ways on how to kill others with fire....
In the medical field, people need to be especially careful not to spread germs. There are a variety of ways to kill them. Some involve fire or at least extreme heat, and it is very effective. Here are two examples. Metal tools can be sterilized by sticking them in an open flame. Biohazard waste gets incinerated. Indeed suffer not for the pathogens to live.
And while it isn't fire, the autoclave doesn't leave behind inconvenient fire residue and can be used effectively to sterilize anything that won't melt in it, and works just fine on liquids as well as solids.
And what this indicates to me, it means that at some point, some person said to himself, "Gee, I sure would like to set those people on fire over there. But I'm just not close enough to get the job done. If only I had something that would throw the flame on them."
Interestingly enough, the flamethrower stopped being used around the time of The Vietnam War, at least by the United States. There were two reasons given: first and foremost, the flamethrower requires an absolutely massive tank for fuel, which slows the soldier prohibitively and told the enemies "Shoot me". Second, the flamethrower isn't really all that useful a weapon; short range and limited fuel keep it from being used at the most useful times. The reason the flamethrower was used for as long as it was (WW1/2 to Vietnam) is because it is a profoundly powerful psychological weapon. Nothing demoralizes an enemy squad as much as seeing your best friend set on fire! The wielder was actually running away with several litres of an extremely flammable liquid strapped to his back.... Unless you get a flamethrower tank, which had its share of combat during WWII.
An indication of the extent to which flamethrowers terrified the opponents is that their operators were usually targeted first and were rarely taken prisoner.
Flamethrowers also were more useful during trench warefare as your targets were so generous to line up in a small space. Which made the fuel issue a bit less problematic. Also, because its rather large area of effect (for a handheld weapon) makes it ideal for taking out things like bunkers. Not very useful in more open combat, like in Vietnam, and utterly worthless in combat near civilians, like in Iraq, but in more entrenched situations it can still be quite useful.
Flamethrowers are also useful against bunkers and armored vehicles, it you can get in close enough. Unlike bullets, the spray of burning fuel only needs to hit an opening and it will splash inside. Being on the receiving end of even a small splash of burning gasoline can ruin you whole day, and even if it never gets inside a bunker the smoke and flame make it almost impossible to see out through the affected area.
In present-day China, they are being used to combat the invading Asian Giant Hornet.
The Raufoss Mk 211 bullet. A specialised round developed for use with .50 BMG caliber sniper rifles, its designed to peirce through armour, explode, and then set the target on fire.
For a more impersonal delivery system, there's incendiary bombs, like those used fairly heavily on Japanese cities during World War II, by the USAAF. The June 10, 1945 "Operation Meetinghouse" firebombing of Tokyo caused more deaths than the immediate effects of either of the atomic bombs dropped in that conflict.
The Luftwaffe firebombing of Coventry wrought so much destruction that Joseph Goebbels coined the term Coventrated to describe the ruined city and many others like it.
Then the Brits used the same tactic against Germany. In the later phases of the war, a first wave of bombers would drop air burst bombs that would blast away the ceramic roof tiles used in German cities and then a second wave would drop massive amounts of incendiary bombs on the exposed wooden roof beams from where the fire would reach the wooden floors and spread to the furniture in the apartments. As in Tokyo, fires were started in specific mathematical patterns that took into account wind direction and speed, which would result in a massive updraft at the center, causing a huge fire tornado and transforming the entire city into Hell. While the fire usually didn't reach the bomb shelters, large numbers of people died from suffocation as the fire consumed the entire oxygen in the air. The incineration of Hamburg and Dresden are the closest thing Germans have to a Hiroshima-trauma. The deaths and destruction from the bombing of Dresden exceeded the nuclear apocalypse on Hiroshima. Recent accounting though has shown the death rate to have been much lower.
Incendiary (often napalm) bombing from planes was extensively used in Vietnam and later conflicts. The US military didn't give up on this trope, they just increased the range. And then there's the bizarre tale of Operation X-ray...
Of the 180 largest Japanese cities that were firebombed by the 21st Bomber Command, 64 were completely destroyed.
Today's flamethrowers are more along the lines of missile launchers that use incendiary ammunition. And then you have the MLRS version. A typical example is the Russian RPO Shmel ("Bumblebee"). This is a tube looking like an ordinary bazooka. Inside is a single-shot rocket filled with napalm, or worse, a fuel-air warhead. A rarer variant, RPO Rys ("Lynx"), is the same, but but you can carry extra rockets and reload it.
The IRA still used flamethrowers for the psychological effect until recently.
Greek fire, an ancient chemical concoction used in naval warfare that burst into flames upon contact with air and can never be extinguished by water. The secret of its formula was so well-kept that it is lost today. The Greek Fire was so useful back in the Medieval period that many historians agree it was one of the main reasons the Byzantine empire lasted for so long. Also, the Byzantine Empire invented flamethrowers in the first place.
Inverted by Hippocrates: "What medicines do not heal, the lance will; what the lance does not heal, fire will."
It is actually a common practice among those who fight forest fires to start a number of monitored brush fires while also cutting down trees. The rationale? Fastest way to get rid of fuel and helps to stop/control the spread of a forest fire by starving it. That's the way nature does it (minus the "monitored" part). In fact, certain types of cone-bearing trees need fire to open the cones. Many of the worst fires were that bad because environmental groups got their science wrong and sued to stop/prohibit thinning. Area grows into a tangle of underbrush and deadfall, lightning strikes, huge zone of flamey badness ensues. The Black Saturday bushfires in Victoria, Australia in January 2009 were partially caused by this. That, and all the arson-lit fires.
The back fire (starting a fire here so that the encroaching fire doesn't have fuel once it gets here) was invented on the ground. A group of fire-fighters were running from a blaze and one of them realized they couldn't escape that way. He stopped and lit a fire, urging his mates to join him. They told him he was crazy and kept running. He was the only one to survive.
The historical Oda Nobunaga (not the demonic, made a Deal with the Devil, comic book Super Villain one that appears in many anime) had a rather disturbing fondness for this. It began with the burning of the Mt. Hiei buddhist temples, (and the slaughter of its thousands of residents) and culminated in the Siege of Nagashima, (another warrior monk stronghold) where he forced the defenders into their entirely wooden inner fortifications, built a wall around said fortifications, then lit the building on fire. Not a single one of 20,000 people inside escaped alive.
This is one of the reasons why Nobunaga was betrayed by Akechi Mitsuhide: As a high-ranking General of the Oda clan and a Buddhist, the torching of the Mt. Hiei temples did not sit well with him at all. Though most adaptations like to portay that trait of Nobunaga as a reason of him being the villain, here he wass actually just a Combat Pragmatist. Do you want to risk the lives of your soldiers in storming a building full of fanatical war monks? Or maybe you'll just advance them hiding in a mostly wooden building to its logical conclusion?
Sadly, this is still a common form of 'jungle justice' in many parts of sub-Saharan Africa, especially in the port city of Lagos, Nigeria. A person caught red-handed at theft or murder is soaked in kerosene or petrol, tires stacked around him/her, and set on flame for an absolutely horrifying execution.
What did Sun Tzu & the Vikings both have in common? The love of fire. It is great for hit and run attacks, as it will continue to cause damage (both physical & psychological) without requiring to stay in the place.
If something won't burn with regular fire, there's always Chlorine Trifluoride. This stuff is so horribly reactive that it can light ashes on fire.
To quote In The Pipeline "The compound is also a stronger oxidizing agent than oxygen itself, which also puts it into rare territory. That means that it can potentially go on to “burn” things that you would normally consider already burnt to hell and gone, and a practical consequence of that is that it’ll start roaring reactions with things like bricks and asbestos tile." One propulsion engineer who'd dealt with it said that the best equipment for working with this stuff was "a good pair of running shoes."
Contrary to popular belief, witches weren't burned in England (or the Colonies, which mostly followed English practice). In Continental Europe, witchcraft was tried as heresy, for which the penalty was burning: but the pragmatic English tried witches for whatever they were supposed to have done with their magic, from murder down to theft and destruction of property, and sentenced them accordingly as the English sentence the common man. So while many witches were hanged, there were also many cases of convicted witches simply getting a fine or just a stern warning. Also contrary to popular belief, this was also the practice in Europe at large. The Spanish Inquisition, for example, was quick to pronounce 'Witchcraft' as 'Insanity' and refused to even consider charges of it. However, many local courts in Spain brought people up on charges of various counts of witchcraft on their own volition, though burning was again only reserved for the most serious of cases. Yet another contrariety to public belief, witches weren't persecuted in Western Europe before the Reformation. The Roman Catholic Church denied the existence of witchcraft and was quick to condemn those accusing others of the practise.
During much of English history, there were only two crimes punishable by burning: heresy and treason. The latter was punished in different ways depending on the offender's status and gender: nobles of either gender were beheaded; common men were hung, drawn and quartered (a rather gruesome form of Cruel and Unusual Death); and common women were burned at the stake (as a public-decency measure; hanging, drawing, and quartering often involved stripping the condemned of his clothes and always included emasculation). Treason came in two flavors: High Treason (treason against the state, including most of what we normally think of as treason, plus sundries such as counterfeiting the King's seal or NTR-ing the King's heir) and Petty Treason (murder of someone with lawful authority over you, most commonly murder of a man by his wife).
Ironically the burning of people for religious crimes was chosen (at least by some, particularly in the Catholic Church) because it was considered the most merciful option in the case of unrepentant individuals. The reasoning being that if you decapitated a person their soul would go straight to hell, but being burnt alive, the victim would have a chance to repent their sins before a priest (who would be standing nearby) and accept God, giving them at least a chance of salvation. Throughout history people do seemingly brutal things for (what they see as) very good reasons.
During the Chilean dictatorship led by Augusto Pinochet, photographer Rodrigo Rojas Denegri and college student Carmen Gloria Quintana were set on fire by the military in the middle of the protests of 1986. Rojas died due to his injuries few days later, Quintana barely survived but was badly disfigured.
This was once actually a medical practice. As late as The American Civil War it was, field hospitals regularly cauterized amputated limbs with hot iron. And no anesthetic beyond whisky and possibly opium. Soldiers often feared hospitals more than death, quite naturally. It did significantly reduce the chance of dying from an infection, but many soldiers didn't care.
Around this time the syringe and first epidermal and then intravenous injections were invented, and Army surgeons immediately turned to injecting wounded with morphine (also purified from opium nearly in the same period). It did its job relatively well as a painkiller, but the lack of understanding in aseptics and proper dosages lead to the explosion of sepsis and opiate addictions.
Quelea are a type of small bird native to sub-Saharan Africa. They are one of, if not the most numerous species of birds in the world. Flocks number in the thousands and are capable of completely stripping grain fields in a matter of hours. How do farmers deal with the problem? They find the trees the birds nest in, wait until nightfall, and use dynamite and gasoline. Boom!
Interestingly, in Egypt, people really did use mummies for kindling, since when there were thousands upon thousands of mummies, they made for a ready source of fuel. Their historical value wasn't considered at the time. Could be a small amount of Fridge Horror there.
A fever is essentially your body try to do this: kill off invasive microbes by creating an environment too hot for them to survive in.
Some kinds of Japanese honeybees use this tactic against the Asian Giant Hornet that can't be killed through normal stinging means, due to it being fast enough to kill a bee before getting stung. The hornet can't survive said temperature, however, but the bees can, so this tactic is actually a lot more effective and costs the lives of very few bees.
How do Eucalyptus trees get rid of other plants that grow around them and steal the precious water in the desert ground? By emitting vapour of the highly flammable Eucalyptus oil while having very flame resistant wood and their leaves high above the ground. Once the vapour ignites, it burns all the small grasses and shrubs while only slightly singing the bark of the trees. Unfortunately, it also has the side effect of causing the trees to explode when struck by lightning.
Rhystysma Acerinum, known commonly as Maple Tar Spot is a fungus that looks like black spots on infected tree leaves. Because it spreads on early spring through leaves infected on the previous year, the recommended cure is to gather all infected dead leaves in the fall and burn them.
This is the final step in any very secure hard disk disposal method. Government secrets and such might be recovered from a drive that is wiped, repeatedly overwritten, and physically broken or drilled through. It probably won't be recovered from the completely chaotic lump of ash and metal left after going through the incinerator.
Also a countermeasure against tampering in highly secure safes and intelligence packages. Unless it's disabled before the package is opened, boom. Sure, you can kill the courier or crack open the safe, but anything inside (and possible anything in the near vicinity) is going to be on fire once the pyrotechnic charge inside goes off.