Mercenaries 2: World In Flames. Apart from the fact it's in the TITLE, you can use fuel-air missiles and fuel-air bombs (delivered by plane) to kill things with fire. A lot of things, with a lot of fire.
Mantorok and Xel'lototh zombies in Eternal Darkness can easily be killed by fire.
Michael Edwards also attempted to use explosives to put out the oil fires in the penultimate chapter.
Subversion: Gibdos in The Legend of Zelda: Majora's Mask. Light them on fire, and... you get a ReDead immediately using its stunning Screech. In most other games, it works just fine — killing them outright, or turning them into a much weaker Stalfos.
Logically, you would expect Keese to be this. You would be wrong. Don't block them with a wooden shield if you prize it.
In the remake of Resident Evil, you have to burn the bodies of zombies you kill (or blow their heads off), or they'll get up again, stronger.
A particular monster in Resident Evil 5 plays this absolutely straight. The only way to kill it? Incinerate it in the conveniently placed furnace. Bonus points for the window that lets you watch as the creature is immolated.
Also in 5, you can use incendiary grenades and flame ammo for a grenade launcher. While they aren't super awesome zombie killers, setting those walking sacks of walking diseased flesh who are looking at you funny on fire really helps, and if they are far enough away then they will die before they get to you.
Also, anything ice based is pretty obviously weak to fire.
Fire is one of the only things that will permanently kill Dry Bones in the Paper Mario series. Curiously fireballs have little effect on Dry Bones in other games of the Super Mario Bros. franchise.
In fact, a long-term fan of RPGs (or possibly video games in general) will often find Kill It With Fire to be the first thing they think of when confronted with a zombie or similarly undead enemy.
This is also true for the MMORPG Ragnarok Online, where fire will deal up to 200% damage against undead enemies. Fire elemental weapons and spells can also be used against ghost enemies to deal 100% damage (unlike the "normal" element, dealing only 25% or even 0% damage). It is also effective against earth elemental foes.
Grass-, Ice-, Bug-, & Steel-typePokémon take double damage from Fire, and the unfortunate Snover, Sewaddle, and Paras lines take Quad Damage, as do Steel/Bug-types and two of the three forms of Wormadam. Paras and Parasect manages to take Quint Damage with its ability Dry Skin. Scizor, Forretress, Durant, Escavalier and Genesect have Fire as their only weakness, but it's a Quad Damage weakness.
It also helps that some of the most popular Pokémon are Fire types. They usually have high Attack and Special Attack stats, plus most Fire-type attacks do a lot of damage.
This is a particularly viable tactic against Shedinja, which can only sustain direct damage from five different types - Ghost, Dark, Flying, Rock, and...well, guess.
The move Fire Fang has the special quality of being able to hit Pokémon with Wonder Guard, even if they aren't weak to Fire normally. While this wouldn't make a difference with Shedinja, it IS a useful way to be able to attack other Pokémon that have Traced Wonder Guard and Pokémon that are hacked so that they are given that ability (which would be useful on a Dark/Ghost cross like Spiritomb because it has no super-effective weaknesses).
One of the more useful Plasmids in BioShock is "Incinerate!" which, with a snap of the fingers, sets people on fire. The random screaming from the affected splicers who've been set ablaze ranges from terrifying to Bloody Hilarious.
Because if mutilated, gene addled psychopaths rushing at you with hooks to mangle you wasn't horrific enough, let's turn them into FLAMING MUTANTS WAILING IN AGONY AND ATTEMPTING TO DISEMBOWEL YOU. Much less frightening.
Taken to another level in the sequel: If you have a Little Sister with you and you use that plasmid on somebody, she'll delightedly scream "Marshmallows!"
The fastest way to kill the first boss of Comix Zone is to get it to light an oil barrel on fire, then push it underneath it and burn it alive.
Half-Life 2 features a few situations where nearby gas tanks can be turned on and the vapors ignited as a convenient zombie solution. Used to spectacular effect in Ravenholm.
In Half-Life 2 Episode One you can use highway flares to light up dark areas, or to light up dark zombies. In one particular situation, you're rather quickly out of flashlight power and flares, so lighting up some zombies is a rather convenient way to get some light.
And then, because after all there is a human puppet being controlled by that headcrab, they scream. And scream. And scream. Just... just shoot him already. To make it worse, this is what they're screaming, played backwards.
Also, in the original Half-Life, one of the Gargantua's weapons was flamethrowers somehow built into its arms. Another alien, the tentacle, is only able to be killed when you turn on a rocket engine above its head and burn it alive.
In Shadow of the Colossus, the colossus Celosia can be held at bay by the hero holding a lit torch, despite the fact that the colossus dwells in a temple with four much larger fires (safely on pedestals) with no sign that it fears them at all.
This fact with the torch is vital to your defeat of Celosia: if you approach it while using the torch it'll back away from you, and this can be used to actually drive it off a ledge. The impact from hitting the ground below breaks the armour on Celosia's back, exposing the vital point. The trick now is getting onto its back while it's trying to charge you...
Mass Effect lets you adapt your weapons with Incendiary Rounds and the upgraded Inferno Rounds for bringing searing pain to your enemies.
High Explosive Rounds not only set their targets (now corpses) on fire, but also do the same thing to nearby enemies in the blast radius, which is about four meters—and sends them flying. While on fire.
The sequel keeps the incendiary rounds and allows tech-savvy characters to launch an auto-seeking fireball via the 'Incinerate' power. Both are useful for stopping enemy health regeneration. There's even an achievement for letting enough enemies burn to death after they're lit up.
Downloadable content for the second game adds a true flamethrower heavy weapon. Short range, but effective against all defenses, and really handy for zomb-er, husks, which usually come in swarms.
Vido Santiago's death if you go Renegade in Zaeed's loyalty mission.
Zaeed: Fry, you son of a bitch.
Mass Effect 3 adds powerful melee attacks to Sheperd's repertoire which change based on class. The Engineer gets a blast of superheated gas surging around his/her arm, letting Shepard bitchslap someone with a flaming backhand.
The flamethrower in the Marathon games is an example—it's extremely effective against mainly organic enemies... less so vs mechanical targets.
Several Mortal Kombat characters use fireballs and such as their special attacks. Quite a few stage fatalities.
Annie in League of Legends has three different ways of killing it with fire, first she can throw a fire ball, second she can breathe fire, and third she can order her teddy bear to attack you (it turns into a gigantic monster that is on fire)
Brand follows this trope to a T, more so than even Annie. In addition, new champ Rumble has a flamethrower attached to his mech, plus a barrage of incendiary missiles. A few other champions have a fire-based skill. Everyone (once you gain a couple levels, anyway) has access to the spell Ignite, as well.
In much of the Legacy of Kain series, fire is one of four reliable ways to finish off vampires (the other three being sunlight, water, and impalement, although some are resistant to sunlight or water).
In Blood Omen you have Flame Sword (which is second only to Soul Reaver itself), Soul Reaver has Fire Reaver upgrade and Fire Glyph, Soul Reaver 2 also has Fire upgrade, Blood Omen 2 has Immolate power, that is given near the end and Defiance has another Fire upgrade. Curiously, it also has Flame Balance Emblem upgrade for Kain, but it only makes mooks fight each other.
In Nosgoth this is the bread and butter of the Alchemist class.
After defeating the demon Melzas in battle, Alundra finally kills him by destroying his body with fire.
The best way to kill Zombies in the X-Com series are with Incendiary/Phosphorous rounds, since these will automatically kill the Chryssalids/Tentaculats inside them.
Both played straight and subverted in Deus Ex: The flamethrower and incendiary phosphor rockets will incapacitate normal humans and the supertough The Men in Black (the latter of which can take a sniper rifle headshot and keep on fighting) with even the slightest graze, turning them into human torches that run around screaming wildly. It is also extremely painful for yourself if you don't happen to have the appropriate anti-Fire implant boosted to maximum, have a fire extinguisher you can use, or have a nearby lake to jump into. However, it has no effect at all on the MJ 12 Commando cyborgs, who need to be taken down by conventional bullets, explosives or melee weapons, and is useless against robots as well.
In Metroid Prime you can kill it with plasma with the Plasma beam, and adapt the beam into a veritable flamethrower as well (sapping away your missiles in the process). Seeing your Space Pirate foes blacken and singe away into dust makes up for the ammunition drain.
In Metroid Prime 3: Corruption, the Plasma Beam makes a return, and when you let a full-charged shot rip into a horde of Tinbots, they melt!
A charged Plasma Beam shot in Prime 1 will also do the same effect of the blackened dust foes. Without the missile draining. The flamethrower is Rule of Cool, but unfortunately, completelyuseless. Ridley tries to kill you with fireballs or plasma beams in most games, plus he uses melee attacks.
World of Warcraft. Mages (Fireball etc.), Warlocks (Immolate), and Shamans (Flame Shock) all have direct fire spells. Hunters can lay down fire-based traps.
Priests have Holy Fire, which used to do Fire damage before later patches modified it into Holy damage instead. It still looks like they're being set on fire from above, though.
The tower of Karazhan has an encounter based upon the The Wizard of Oz. The Straw man hits fairly hard, and has a crippling weakness to fire, though not in the For Massive Damage sense. When a fire spell is cast on him, he has a high probability of simply running around in fear, unable to attack any of the raid. Many groups will have a caster dedicate themselves to spamming Fire spells on him.
Subverted in early raids since everything was immune to fire.
To help fight off the Mantid, the Golden Lotus have set up oil traps on the Serpent's Spine to pour oil on them, and set them on fire. Players taking part in a daily quest can also earn an achievement for killing 60 Mantid with a single torch.
In City of Heroes, nearly every Archetype has Fire powersets to choose from, and all have the common theme of being all damage, all the time. Most enemies are fairly weak to fire for that matter. Ask any Fire/Fire Blaster...
With the sole exception of the Thermal Radiation powerset, which is a case of Heal It With Fire.
In the Back Story of Planescape: Torment, a group of wizards try to do this to Ignus by making him into a living conduit to the Elemental Plane of Fire. It didn't work. It made him happy! Ignus also plays this trope out against his enemies- all of his default spells (which are unique to him) are fire-based, and his default attack is throwing miniature fireballs at his opponents. A Wizard Nameless One can also allow Ignus to subject him to a Death of a Thousand Cuts version of this to gain some of Ignus's spells, by allowing Ignus to burn first a finger, then a hand, then an eye, then the Nameless One's intestines, to charred meat and ash. Except for the last one (you get a spare set if you allow the crazy dissectionist Marta to cut your guts open to see if there's anything of value inside of you), all of these are done to you while the parts you sacrifice are still attached to you.
Halo 3 brings you unlimited fun with the flamethrower and flame grenades. The latter tend to be so powerful they kill most enemies on contact and burn through the heaviest Brute armor and Flood forms in seconds.
In Halo Wars, the Earth Forces have found that while the Flood is an extremely dangerous threat, flamethrowers are excellent weapons against perhaps the worst most serious menace of the flood spore creatures.
In Call Of Cthulhu: Dark Corners Of The Earth, the player encounters a shoggoth at one point. At first, the player attempts to dispatch it with electricity. But this doesn't work out so well. How do you kill it? Easy. Start a gas leak, leave the room, turn the power back on (there are live wires exposed in the room the shoggoth is in), and let the horrible monster be burned to a crisp by the ensuing explosion. You even get to walk through its charred, smoking, gooey remains!
Insect creatures tend to be weak against fire in RPGs. Hornet Man's weak point is Magma Bazooka.
Fire Emblem. Eliwood's most powerful sword has the element of fire, one of the better anima tomes is called Elfire, and mages first start using fire as their weapons. This game is just loaded with this trope. The Fire Emblem's namesake item in every game tends to be a powerful seal for evil Gods.
FE 4: Emperor Alviss'sRoyal Fire Knights— a division of elite soldiers dedicated to this trope. You first see them in action when they kill the enemy's reinforcements in Chapter 5. Then they kill your units at the Battle of Bahara. When you finally fight them in Chapter 10, they're Demonic Spiders. The apple isn't falling far from the tree, Emperor Alviss himself wields a spell of Holy Fire: Falaflame. It's extremely powerful.
Several baddies in T'ai Fu: Wrath of the Tiger are able to be quickly dispatched by fire, including — bizarrely enough —stone mantis statues.
Dead Space has a flamethrower. In a subversion, however, it's more useful for discouraging necromorphs from getting close, rather than killing them; it takes a prohibitive amount of ammunition to actually kill one with a flamethrower — they're resistant to most forms of damage except being dismembered, and when's the last time you saw a fire take someone's arm off?
Played straight in the case of the Hunter, which is proven to be nigh invulnerable to all of your weapons, is only killed when it gets hit by the engine fire from the Ishimura's executive-use shuttles.
The flamethrower got an upgrade in Dead Space 2. Now it is a lot more powerful, and causes lingering damage. Also they are perfect for killing swarms of little Necromorphs.
The Flaming Arrows upgrade in Age of Empires makes arrows much more effective against buildings and ships. The first two games in the series also featured ships with flamethrowers. Age of Mythology also has some fire-based myth creatures such as the Norse Fire Giant or the Egyptian Phoenix. One of the Norse god powers is Flaming Weapons, as well.
All 4 Fallout games have incendiary weapons: the traditional flamethrower (flamer), Molotov Cocktails (in the first two games), Nuka-Cola Grenade (a radioactive molotov cocktail with even more explosive results)... and all of those weapons set their foes on fire with a critical hit (or with any hit using a Flamer) before turning the corpses into piles of ash. The 3rd game has flame-spitting giant ANTS. The games just LOVE this trope.
The Molotov cocktail returns to New Vegas as the Fire Bomb in Honest Hearts, and Old World Blues features a sonic emitter pistol that causes people to catch fire. Lonesome Road DLC features the flare gun, which expends flamer fuel to fire a magnesium flare that very reliably lights things on fire, perfect for scaring off tunnelers, deathclaws, and other nasties.
.50 caliber anti-materiel rifle rounds are available from a few vendors in New Vegas—including specialty loads like the incendiary round, when you positively have to shoot something with the largest ballistic round in the game and still have it catch fire afterwards.
Gears of War 2 gives you access to a flamethrower, which is one of the nastier close-range weapons you can use, doubly so because of its effectiveness at getting around enemy cover. It also does a ridiculous amount of sustained damage, making it great to use to hose big, slow enemies like Boomers, Maulers, and Reavers.
In Gears of War 3, the flamethrower is one of the only weapons that has any effect on a Berserker.
Call of Duty: World At War allows you to use a flamethrower to set enemy troops on fire. Unlike the flamer in United Offensive, this one has unlimited ammo (although has an "overheating" gauge), which means indiscriminate burning death to any hapless enemy soldier. Even one mission is called "Burn Them Out" and starts off with you burning everything with said Flamethrower. Another mission gives you Molotov Cocktails.
Black Ops has a flamethrower attachment for assault rifles.
After building the Temple of Planet late in the game, you get this quote from Academician Prokhor Zakharov from "the Lab Three aftermath"
Let the Gaians preach their silly religion, but one way or the other I shall see this compound burned, seared, and sterilized until every hiding place is found and until every last Mind Worm egg, every last slimy one, has been cooked to a smoking husk. That species shall be exterminated, I tell you! Exterminated!
The Chinese faction from Generals have a similar love for fire. They've got flamethrowers, incendiary artillery shells, incendiary bombs, incendiary air-launched missiles, and if that doesn't solve the problem, it's time to switch to nuclear fire.
Dynasty Warriors loves this. It's almost as if the strategists are limited to either using fire to burn things down, or ambushes to surprise the enemy.
In the Shu campaign, Zhuge Liang's debut battle consisted of him setting traps in a forest. The first one to be triggered was... yes, it involved setting the enemy on fire!
In the Battle of Chi Bi/Red Cliffs, Cao Cao's enormous fleet outnumbering the Wu and Shu forces by something like ten to one was defeated by Zhuge Liang and Zhou Yu hatching an intricate plot to burn his ships, then strike back.
The fire spam gets ridiculous when you get to the Nanman Campaign and meet the armoured soldiers who seem to be invincible to your troops. A few minutes later, you can't help but laugh at Meng Huo's troops wearing wooden armour as Zhuge Liang uses fire yet again to win that particular battle. Worse, this battle happens after Chi Bi where the Shu strategist showed the whole of China without any doubt how good he was at using fire to burn things that belonged to the enemy!
The Burninator flamethrower in Vampire: The Masquerade – Bloodlines is so powerful against every other thing in the game it makes the player feel kinda dirty for using it. One specific example is a sniper boss whose main power is the ability to teleport away and lay down a couple hits before you can get close. The flamethrower disrupts this ability and saps his health even faster than some mooks. Every enemy in the game — except for the Sheriff — is a pushover when you bring FIRE into the picture. This is based on Old World of Darkness rules (listed under Tabletop game)
The Bubble Bobble games have fire-filled bubbles which are strong enough to kill enemies but weak enough to stun the protagonists. Just, well, touching anything of a higher firepower (enemy fireballs) will incinerate the protagonists.
Incendiary ammo in the sequel makes your main weapon have one whole clip of fire bullets, instantly killing common infected with fire while lighting up special infected and watching them burn for a while. You can even use incendiary rounds in a friggin' grenade launcher and watch a horde explode and rain down in firey bits!
You have to Burn the Witch! with a molotov cocktail to unlock the achievement, Burn The Witch.
In The First Funky Fighter, a bonus item on stages 1 and 3 will, when hit, cause a firestorm that destroys every enemy on the screen.
Several Mega Man Robot Masters, including the obvious (Fire Man, Heat, Flame, Burner, Magma, and Solar), and the somewhat less so (Pharaoh, Turbo, Sword), though not Napalm Man. When Mega Man wants to Kill It With Fire, using it against the ice-wielding guys is a bad move (Except in 6, Mega Man 8 and 10 where it does the same damage as a charged Mega Buster). Oddly enough, you'll use fire against the guys trying to cut you to bits (Ring Man, Slash Man) or slinging explosives around (Bomb Man, Burst Man, Pirate Man).
In the Mega Man Zero games, weapons boosted with the flame chip are indeed extremely effective against ice opponents. (In 2, it is also extremely therapeutic, given that the boss you had to kill to get said chip was a real pain.)
Mega Man Star Force has a number of fire-based opponents, plus the Saurian tribe in 2, and a fair number of attacks. The "Heat Grenade" deserves special merit, since not only does it blast apart the three back rows with significant damage, but it also destroys any special scenery on those squares, such as grass.
In Far Cry 2, a First-Person Shooter set in modern Africa, fire is realistically implemented: many things can cause one to start (gas tanks, fuel barrels, flamethrowers, Molotovs, flare guns, the backblast from rocket launchers, and any sort of explosion) and depending on your surroundings, it can spread, fast. Aside from obvious uses like setting people on fire, enemies also react accordingly, and will back away and avoid fires, making them good distractions, allowing you to flank them, sneak into their base, or escape. Seeing an outpost up in flames, spreading across the grass, up trees, and into the jungle as far as the eye can see, is a sight to behold.
In Starcraft, this is how the Confederacy dealt with its rebels, and how the Protoss dealt with Zerg-infected planets.
Thanks to the Firebat, it's also how the Terrans deal with Zerglings, Zealots, other Firebats...
The sequel adds to the Terrans' arsenal the Hellion, a speedy four-wheeled craft with a flame thrower. The two are later merged into the Hellbat, with bonuses against light ground units...which just so happens to include all worker units.
The flamethrower is one of the most effective weapons in Syndicate, especially early in the game. It also causes the victim to thrash about in pain and set everything he touches on fire... Hilarity Ensues.
In Samurai Shodown II many characters in that game can, in some way shape or form, torch you. There's 17 total, and counted 11 (plus the support character) can leave you in flames. Toasty!
Build furniture from flammable materials, then set them on fire as an incendiary floor trap. Notable, Artifact items can catch on fire but are indestructible, and will therefore burn forever unless extinguished with water.
Capture and tame a dragon before it can taste dwarf blood and you have a hellbeast capable of breathing flame (although surprisingly, it isn't immune to fire, meaning particularly stupid dragons tend to incinerate themselves).
Magma. On the forums it is often remarked that magma solves everything, including, in one case, as a solution to a burning dwarf: if he's melted, he's not on fire anymore. Popular methods include:
Use carefully placed reservoirs to drop magma on invaders from above.
Use massive towers of pumps to build up the pressure to create magma geysers from below.
There are things that can't be killed by heatnote heat only damages by causing a creature's layers of fat to melt, which causes bleeding; creatures without fat or blood are thus immune to heat, and some of those can't even be killed by weapons due to a quirk of the injury system. Yet magma can still stop them if you submerge them in magma, then submerge the magma in water, which turns the magma to obsidian and crushes anything within it. One player used this method to defeat the entire population of hellusing only a massive checkerboard shaped Death Trap.
In Minecraft, this is an effective tactic to kill mobs from a distance, lighting the ground on fire and having them walk into it.
You can also place blocks of wood or, even better, coal to use this tactic in places that aren't normally flammable, such as caves.
The Elder Scrolls IV: Oblivion has several undead (including vampires) as well as trolls and high elves with a vulnerability to fire. But as the locals will frequently tell you, "a sword works just as well".
In Skyrim, of the three energy types used in Destruction magic, fire is noted as simply being the single most damaging, and works best overall for when you need to kill something fast. The other two energy types have their uses (cold saps stamina and slows enemies down, and shock drains magicka) but nearly everything worth shooting with magic in the first place is either damaged normally by fire or has a specific vulnerability to flames. It has the added benefit of panicking targets at low health as well.
Furthermore, both dragons and the player character have access to fire based Shouts that allow them to wield fire against their enemies.
Space Colony has flamethrowers to deal with fast growing plant life and insect infestations.
You are forced to euthanize your faithful Companion Cube in Portal by throwing it into an Aperture Science Emergency Intelligence Incinerator. Later on, you do the same to GLaDOS, in an act of sweet revenge (seeing as nothing else works and the game's second incinerator is conveniently located in the same room).
GLaDOS tries to do this to Chell.
"I'm not even angry. I'm being so sincere right now. Even though you broke my heart and killed me. And tore me to pieces, and threw every piece into a fire. As they burned it hurt because I WAS SO HAPPY FOR YOU!"
In the Contra series, the usefulness of the flamethrower depends on how it works in that particular game. First two games, it kind of sucks, but the third game, it's fucking awesome.
In Hard Corps: Uprising ('successor' to the Contra series), the 'Heated Plasma' weapon launches out a short-range, high damage fireball that burns through enemies in a very satisfying manner. Even better: That's just one way to use it. Charge it up really quick to unleash a -giant- ball of fire that devastates enemies, travels through defenses, and best of all, travels all the way across the screen unlike its normal shots. Because that isn't awesome enough, it is available in Level 1, 2, and 3 forms, each upgrade increasing the damage and size of your fire.
There's even a side mission in the game that requires the player to kill X amount of Triads with a flamethrower before the clock runs down.
And in San Andreas, with it's trusty throwable cousin, the Molotov Cocktail. Plus, ANY explosion will cause fire.
Company of Heroes practically owes this trope money. To wit: the first heavy weapons that the Americans and the Wehrmacht can get just happens to be the flamethrower upgrade, turning builder units into soldiers to be feared. From there on, the Americans can eventually get the Sherman Crocodile flamethrower tank (aka the Napalm NASCAR, while the Wehrmacht can upgrade their halftracks with twin flammenwerfers and lay fiery waste to entire swathes of land with their Nebelwerfer rockets and Firestorm incendiary artillery barrages. The Panzer Elite don't get flamethrowers, but they can lay incendiary booby traps as well as loft incendiary grenades and mortar rounds. The Brits are perhaps the least burn-happy of all 4 factions, but their sole flamethrowing platform - the faction-specific Churchill Crocodile - is a final-tier unit that gets to fire its main gun as well as use its flamethrower.
Fire Shark has the red flamethrower weapon. At max level, it shot out 6 streams of very damaging fire, two of which fired out forward and the other four swept the sides and back of your plane, easily massacring every mook in sight. There's a reason why the game is called FIRE Shark...
In Sacrifice this is naturally the chief weapon of Pyro, god of fire. He has exactly one unit that does not use fire in some fashion, and every single spell involves fire. Even the "defensive" spell Pyro offers does nothing for your defense, and instead just sets you on fire, damaging nearby foes while you are conveniently immune.
Age of Wonders uses quite a bit of fire. Numerous units enjoy the Fire Strike ability, letting them deal fire damage to foes, while the fire school of magic does exactly what you'd expect. The first game also featured flamethrower siege engines, originally invented by the dwarves but buildable by anyone.
In Dragon Age: Origins, the darkspawn are weak against magical flames, along with walking corpses and sylvans. However, there are a few creatures completely immune to fire.
Dragon Age II increases your friendly firing fun with Apocalyptic Firestorm, which rains blazes over 10 meters for 10 seconds. The less devastating Combustion Grenade includes a helpful stun effect that can work against fire-immune beings.
The Flashpak, in Wing Commander IV, destroys ships by igniting their internal atmosphere, burning them out from the inside.
Team Fortress 2 has the Pyro, who focuses on this trope. The primary weapon is a Flamethower, natch. Alternate weapons include a flare gun for harassing foes far away, a fire axe for a melee weapon, a special fire axe that deals critical damage to burning enemies and another special axe that sets ablaze everybody it hits.
Sniper using the Huntsman can also get a light from their Pyro buddies, giving them flaming arrows.
This is also the best method for sniffing out Spies. Even if they have the Dead Ringer (feign death watch) you can still light 'em up, and it's very satisfying when you do.
Meet the Pyro makes killing things with fire both dark and sinister, as well as magical and fun!
In Knights of Honor, one skill your marshalls (Generals) can learn makes archers and siege Weapons more powerful by, obviously, lighting them on fire. you even get a special animation of the enemy troops freaking out, and rolling on the ground before they die from the fire.
Dito for the cauldrons of burning oil. nothings quite as satisifying as half the enemy army burning at the gates.
Time Shift has the Hell-Fire, a sub-machine gun/flame-thrower combination with incendiary ammunition.
In ''Solatorobo', Baion's Mini-Mecha, the BERIUS P-2, is specialized in killing things with fire. Certain other minor enemies as well, plus flamethrower traps placed here and there.
In Wasteland Empires on Facebook, fire weapons (Units called Arsonists and Fireflies are the two main ones, along with your various scrapyard cycles, bomber planes and helicopters)are the easiest and most effective way to take care of mutant outposts. And although different enemies have different items that work best against them, fire is always good to bring with you whoever you're fighting.
In Dark Souls, fire kills a lot of things (including you) quickly. The game offers plenty of options for fire damage too — most offensive pyromancy consists of different ways to burn things magically, charcoal pine resin can be applied to normal weapons to temporarily set them aflame, and weapons can be forged to deal fire damage or chaos fire (which increases based on humanity). Plenty of enemies also use fire, such as some mooks that wield torches instead of normal weapons.
Brutal Legend gives us the Baron, a motorcycle-riding pyromanic bad-ass and leader of the Fire Barons. According to Mangus, they were a group of outlaws that burned whatever they wanted and fled when Lionwhyte took over. They return and team up with Ironheade after helping them defeat the Drowning Doom, which gives rise to one of the most boss lines in the game:
Baron: Burn the other guys!
In Baldur's Gate 1 and 2, you have access to a surprising number of fire-based spells, useful for killing trolls and, um, everything that gets within fireball blast radius. Especially funny if you get the Summon Fire Elemental spell (ideally with a druid like Jaheira, since they don't have to worry about it breaking free and trying to kill them, unlike mages) before going to the ruined temple in the Umar Hills quest, since the elemental is immune to the attacks of nearly everything in the main level of the ruins, allowing you to clear the whole place out without breaking a sweat.
Not so much for killing, but the PlayStation Vita version of ModNation Racers weaponizes fireballs as a power-up. The thing is, because stacking power-ups increase their level, you can max it out at level 3 and fire a giant Phoenix to swoop across the track.
The Plasma Burst Generator in X3: Terran Conflict is a pirate-designed fighter-scale weapon that is effectively a flamethrower IN SPACE! It emits a broad cloud of superheated plasma that is murder on small ships and can do serious damage to capital ships due to Splash Damage Abuse. It's the only weapon to get a unique achievement, "Turn Up the Heat", for scoring twenty kills with it.
Another pirate-designed weapon is the frigate-scale Incendiary Bomb Launcher, which does burn damage when it hits.
There's always a chance the randomly-generated weapon you just picked up in Borderlands will add fire damage, which does increased damage to fleshy (unarmored, unshielded) enemies and adds damage over time when it hits. There's also fire barrels that explode into a burst of flame when shot, and fire-elemental grenades to spread the damage across a large area. Elemental Relics can cause a character's special skill to deal a particular type of damage as well, and this includes Fire Elemental relics. Vladof-made shields will explode in a wave of fire when depleted to harm enemies.
The sequel, Borderlands 2, includes all the previous examples, but also includes the playable Psycho, Krieg, whose "Hellborn" skill tree revolves around enhancing the effect of fire to deal huge amounts of damage while also setting himself on fire for the duration. He can breathe fire as a special skill and can even spawn homing fireballs when injured. A legendary shield, "Flame of the Firehawk", constantly emits waves of flames when it is depleted until it recharges, unlike its common kin which fire once, then must recharge.
Spec Ops: The Line features white phosphorus mortars, which are a form of incendiary rounds. The effects of the phosphorus is horrifying - true to its real life counterpart.
Thief: Although not nearly as effective as holy water, fire-based attacks can kill undead foes (except for Flame Shadows or Fire Elementals, for obvious reasons). Fire arrows and explosive mines are Garret's most powerful weapons in general, though since the game is based around avoiding combat as much as possible, they generally don't see that much use.
This is the raison d'ętre of the Firebug class in Killing Floor While he uses conventionnal gunsnote a modified revolver that shoots distress flares, a Mac-10 SMG, a shotgun and a WW2 flamethrower save for his endgame toys, he fires incendiary ammo that will set ablaze anything touched by it. Very useful in the fact that, despite doing pinch damage to them (and only them), fire damage won't trigger the "charge" flag of the Scrake or the Fleshpound, meaning a high-level Firebug can solo those two horrors by hitting them with a single bullet and letting fire do the job (and eventualy lighting it up again as fire stops after a while).
BLOODCRUSHER II's fire elemental damage does damage over time to anyone hit.
In After the End, the only way to harm and kill the Sentinel boss is to push it in a conveniently placed furnace at the end of the room taking advantage of the enviroment and your newfound powers. However, when the lifebar reaches 0 the beast will still burst from the furnace... only to drop dead from the burning flames.
The Scorchers in Crysis 3 and their Incinerators do Exactly What It Says on the Tin. The database entry says that the Ceph came up with them deliberately to capitalise on Earth lifeforms' vulnerability to heat.
FTL: Faster Than Light features the fire beam and the fire bomb as dedicated fire-causing weapons, as well as the potential for any sort of weapon hit on a ship's hull to cause a fire. There's great fun to be had abusing the fire beam particularly, since you get an achievement for setting the entirety of an enemy ship on fire and only one race is immune to fire (and even then, they have to put them out). On anything but an AI-controlled ship (which has no oxygen), an out of control fire is effectively a death sentence.
Rock crew are immune to fires, and therefore are great for suppressing fires on your ship or augmenting fire weapons directed at the enemy ship. Fighting enemy crew in a burning room will rapidly deplete their health, and once their health is critical they will automatically run away, leaving your Rock invaders free to destroy whatever system is in the room if the fires haven't destroyed it yet. In fact, the Type B Rock Cruiser starts with Fire Bombs; buy a teleporter, drop bombs into an enemy ship, and beam your crew in, and the rest is history.
In A Hat In Time, the Snatcher's only weakness is fire. Fortunately, the Subcon Forest is also home to Fire Spirits...
Gunstar Heroes has the Fire Shot basic weapon, which is your typical short-range, high-damage flamethrower...to start. As you pick up additional weapons, you may combine weapons to access some useful upgrades, including a rapid-fire grenade launcher, a controllable fireball, an even bigger and longer-ranged flamethrower, and finally what can only be described as a lightsaber in all but name. The fire/fire combo deals the most damage per second at a reasonable range, and is the go-to weapon for clearing out large numbers of mooks.
A Zero Punctuation fan-game made for the Stonking Great Zero Punctuation Game Contest was a Beat 'em Up that used, among other things, a Guitar Herocontroller for melee attacks as well as a variety of guns. However, the most effective weapon far and away was a simplified version of the aforementioned Far Cry 2 flamethrower, which the game's star himself described thusly after playing it.
There are several units in March Of War armed with flamethrowers. Biggest ones are probably the Republican Flame Tank, the Soviet Union's Inferno Hammer and the Shogun Empire's Flame Tank.
Serena implies this as the final fate of the protagonist, even though he most likely is already dead...
Ib: This is the only way to absolutely, truly, destroy paintings in the Fabricated Gallery. It's also how you kill Mary at the end of the game, usually. Any other attempt to destroy her painting is ineffective. The whole thing is very nicely foreshadowed by a friendly sign reading "No fire in the gallery", and a whole room freaking out when Garry tries to use his lighter to see in the dark.
In Town Of Salem the Arsonist uses this method to try and eliminate Townies and Mafia alike. At night, he douses them in gasoline, waiting until he has enough to set them alight. The worst part? Not even the night immunities from Serial Killer and Godfather will protect them.
Strife has both the Flamethrower and White Phosphorous Grenades. The Flamethrower is better than most video game ones, but still rather lack luster. The grenades, on the other hand, have a lingering burn effect that can easily dispose of even the toughest mobs in a matter of seconds.
In Gruntz, the Welder's Kit tool. It shoots a fireball that is an instant kill to any grunt except the ones wearing Gunhats.