"You know, Dick, if I had my way, I'd meet Rommel face to face; him in his tank and me in mine. We'd meet out there somewhere... salute each other, maybe drink a toast, then we'd button up and do battle. The winner would decide the outcome of the entire war."
This was done to avoid bloodshed in Basilisk: Two rival Ninja clans fighting with several selected representatives on behalf of the Ieyasu brothers to see who earns rule of the shogun (based on an 20th-century Japanese novel).
In G Gundam, the Gundam Fight is a tournament that the space colonies use as a substitute for war, each colony sending one Gundam fighter to represent them.
Occurs on a small scale in the "Twins' Guards" episode of GUN×SWORD: a town split into two factions hires Van and Ray to fight each other. The fight is supposed to settle a dispute over an inheritance without further loss of lives of the warring townspeople.
War between the two main nations of Last Exile usually takes this format. A bunch of Red Shirts with muskets line up and shoot at one another from a single ship; whoever has the most survivors is declared the winner of the battle. Only if the results are inconclusive does a full naval battle begin.
The Otome system in Mai-Otome works this way in both the anime and manga continuities. An Otome is far more powerful than conventional military forces, and if she dies, so will the leader to whom she is contracted.
In the manga, the dispute between Cardair and the Aswad is settled by having Akira fight Arika, but this is interrupted when Natsuki intervenes and forces the duel to stop.
Defied in Mobile Suit Gundam Wing. When Treize challenges Zechs to a duel to decide the outcome of the titanic battle that is about to start, Zechs refuses, claiming that the nature of the conflict is too serious to be resolved by a single duel.
In Medabots episode "Ban All Medabots", a bunch of medabots attacked the school the main characters attend and the students got their medabots to defend it. During the fight, Rokusho showed up, told them an all-on-all battle would get too many people hurt and suggested each side should pick one to represent them. They agreed.
In Popcorn Avatar, the war between the Asura and the Deva proceeds with both sides using "avatars," normal humans they choose to bestow their powers, to fight their battles.
In Banana Fish, Ash faces his traitorous lieutenant Arthur in one-on-one combat, in order to prevent a long and bloody gang war.
In "The Travelers", this is actually how all of the kingdoms prefer to do battle, because of the terrible consequences of war. Unfortunately a false champion results in war anyway.
Then oddly subverted at the end, when the real champion challenges EVERYONE in the opposing armies to single combat to decide the war. No one calls him on this, and his friends are amazed that he managed to bluff so many people.
In Battleground: Tatooine, the Rogues and some Imperials both want a smuggler, and the smuggler's relative has been well-bribed by both sides and can't decide who to hand the smuggler over to. The Rogues are smallish pilots, the Imperials are enormous seasoned troopers, so there's no truly fair form of combat. So two from each side are armed with a Blade on a Stick, allowed to inflict non-lethal injuries, and told to compete to reach a specific goal. This still◊ favors the Imperial troopers, and they win, but ultimately it doesn't matter.
Angel tries to do this to the Demon Lords of Los Angeles in Angel After The Fall - just him against all their champions (including a tyrannosaurus rex). His friends step in when it seems clear he's getting his ass kicked, and from there it basically turns into a free for all.
Happens in one storyline of The Legend of Zelda comics, when Link has to defend the Queen of his homeland of Calatia against a would-be usurper.
In Scion, the Heron and Raven kingdoms have fought for generations. 200 years prior to the start of the series, the kingdoms' fleets fought at sea and were caught in a storm that washed the combatants onto an island. The fleet commanders fought mano-a-mano while their comrades watched. Neither individual would yield, though. Eventually they agreed to call a truce, not only to their fight, but to the war itself. The island eventually hosted an annual ritualistic combat tournament between the kingdoms to replace actual combat and to keep the peace. It's in this tournament that Ethan and Bron meet for the first time, in head-to-head competition.
A Silver/Bronze AgeSuperman comic featured one of these as part of Krypton's history. In its early days, the planet didn't rotate in the right fashion to support life, so the two largest Kryptonian tribes each selected a champion to decide who would have access to the last bits of food and water. During the fight, their weapons got tangled in a way that helped them discover a means of altering the planet's rotation, thus turning the planet into a paradise. Again, Silver/Bronze Age.
In the second Superman comic ever the Man of Steel ends a war in South America by abducting the chief general of both sides and ordering them to settle the issue between themselves. At which point it gets revealed that neither side has anything against the other and the war was started by munitions companies to up their sales. The generals shake hands and the war ends.
Near the end of Archangels: The Saga, the Big Bad challenges God's decree that the human soul he's been trying to damn has been taken out of his reach forever. God responds to this challenge is by summoning Michael the Archangel to battle the Big Bad in a one-on-one fight. Michael and the Demon's base powers are evenly matched, but when they each draw on the power of their master (God for Michael; Lucifer for the Demon), Michael ends up winning because his master is the stronger of the two.
In a Carl Barks story, the Duckburg branch of the Junior Woodchucks and the Goosetown branch participated against each other in several events. After the last event, each branch had an equal number of victories and it was decided their instructors would decide the competition's winning branch by having a boxing match against each other. Unfortunately, the Duckburg branch's instructor wasn't available and Donald Duck had to be their stand-in.
In Superman & Batman: Generations, two Epsilon Eridaniites are looking for a suitable champion among the two they have seen on Earth — Superman and Batman — to help defeat the Borta, and enlist the aid of the World's Finest nuisances, Mxyzptlk and Bat-Mite, to test both of them out. However, to ensure that it would be a fair fight, Mxyzptlk must test out Batman while Bat-Mite tests out Superman.
In Superman VS Muhammad Ali, an alien race offers to pit their greatest champion against Earth's, winner take all. To decide Earth's champion, Superman and Muhammad Ali had to face each other in a ring with red sunlight lamps to take away Superman's powers and make it fair. After Ali won, he faced the alien's champion in the ring. Ali won, but the aliens dishonorably tried to invade Earth anyway, only for Superman to reveal he anticipated their treachery and sabotaged their fleet.
In an ABC Warriorsflashback story, the UN passes a resolution that all international wars be settled by a duel to the death between the leaders of the nations in question.
The battle in the beginning, Boagrius is set to fight against Achilles, but dies within seconds.
Subverted by Paris and Menelaus. Paris flees the fight and Hector interferes and kills Menelaus. The battle was pointless anyway, as pretty much everyone except Paris point out the invading army would attack whatever the outcome. Menelaus at least claims he's doing it to regain his honor, which was sullied when Paris took his wife.
The gang war between the Jets and Sharks in West Side Story was to be decided by having a rumble between the two gangs. Tony manages to have the rumble settled via a "fair fight" between the best fighter from each gang, Ice from the Jets and Bernardo from the Sharks. It doesn't turn out so well for Bernardo.
The Right Stuff evokes this trope, but it's unique in that it describes (in painful detail) how many test pilots died in combat against an inanimate object, the sound barrier.
Alice in Tim Burton's Alice in Wonderland, against the Jabberwocky, the former on the White Queen's side and the latter on the Red Queen's. And then the Mad Hatter intervenes and general melee ensues, armored cards on the red side, chess pieces and Alice's friends on the white side.
The Chroniclesof Narnia: Prince Caspian had Peter offering single combat against Miraz. He wounds Miraz, but lets Caspain decide Miraz's fate. Caspian spares Miraz, but one of his advisers kills Miraz with a Narnian arrow to make it look like Narnia cheated.
In both the film and the book, the duel is actually a feint. Peter and Caspian know they can't defeat Miraz's army, and the duel is merely to distract Miraz (by challenging his honor) until Aslan arrives. In the book Peter doesn't give the choice to Caspian, but the advisers still kill Miraz and frame Peter for using "dirty tactics."
At the end of The Postman, General Bethlehem and The Postman decide the war by fighting each other. "Wouldn't it be great if wars could be fought just by the assholes who started them?"
In a way, Pirates of the Caribbean: At World's End. Hundreds of pirate ships! Hundreds of EITC ships! Yet the battle is only disputed by one vessel of each side (the Black Pearl and the Flying Dutchman) - the maelstrom is partially guilty for this, but...
In Homer's Iliad, Menelaus and Paris fight a duel, but Aphrodite spirits Paris away when he starts to get the worst of it. Later, Hector and Ajax, son of Telamon, duel all day to a draw, and exchange gifts afterward. Ultimately none of the duels fought during The Trojan War resolve anything.
In C. S. Lewis' Till We Have Faces, Orual herself fights the neighboring prince over his brother, who had taken refuge in her kingdom. Since she kills him, making his brother king, it does settle it.
Peter and King Miraz in C. S. Lewis' Prince Caspian. Some treacherous underlings on Miraz's side turn it into a battle.
In Hilari Bell's Farsala Trilogy, the commander of the Farsalan army offers a duel at the end of the book. Unfortunately for him, the Hrum commander cheats and just shoots him down in cold blood. He DOES agree to a duel at the end of the trilogy... but only because he knows Sorhab doesn't exist. And when somebody DOES take him up on this offer, he still plans to cheat.
In James Swallow's Warhammer 40,000Blood Angels novel Deus Sanguinius, single combat is proposed as a test of whether Arkio really is Sanguinius reborn. Mephiston is about to accept when Rafen declares it his place, and Mephiston steps aside for him. The Inquisitor Stele manages to turn it into a general battle, but Rafen still goes after Arkio and defeats him.
The BattleTech novel Wolves on the Border has the Kuritans fight a series of honour duels against Wolf's Dragoons in this manner rather than a full scale battle. At least to start with anyway.
This is also a common part of Clan culture in that universe. Because of their emphasis on individual honor and glory, there's a strong tendency to keep forces as small as possible (while still achieving one's objectives, of course) and settle disputes in single combat between champions every so often. Perhaps the most famous example was Natasha Kerensky's bid to take the planet Rasalhague Gunzburg with a single warrior...
In Anne McAffrey's Dragonflight, Leesa (rightful heir to Ruatha) maneuvers F'lar (a bronze dragonrider) into becoming this against the illicit Lord Fax. However, she ends up being the victim of her own scheme, in an unusual way.
Romance of the Three Kingdoms. Most battles seem to be determined by duels fought between the commanders on opposite sides, as the winner's troops gain a morale boost and many of the defeated commander's troops would desert. Gan Ning is notable for shooting a challenger before the duel could commence.
Deryni Rising, Kelson responds to Charissa's challenge of his right to rule Gwyenedd by offering this form of combat. His Champion, Duke Alaric Morgan, defeats hers the traitorous Lord Ian Howell, but she and her wounded champion contrive to injure Morgan afterwards and she issues a second direct challenge to Kelson.
The ending of High Deryni involves Wencit of Torenth demanding a four-on-four duel arcane in the sight of the combined armies of Gwynedd and Torenth. Things do not go as planned.
Years later in The King's Justice, Sicard MacArdry asks for single with Kelson to end the war with the Mearans, and Kelson refuses.
The climactic battles in the Redwall books Lord Brocktree and Salamandastron. Both times it's done when the mountain is under siege by the vermin, and the Badger Lord offers to do the single-combat way to cut the war short and save his followers. Badger Lords are made for this trope, since they're honorable to a fault, but also really really hard to defeat.
Also in Mattimeo, when Matthias fights the Wearet. Noteworthy for turning into a battle anyway when Matthias lost.
The cannibals in Nation decide whether to attack by single combat between chieftains, believing that the winner is the one favored by the God of Death. Of course, since they eat and enslave those they attack, the native tribes themselves presumably don't just give up if their champion loses.
Several people have challenged the person besieging their castle to single combat to determine whether they surrender. The problem is no-one seriously believes the losing side will surrender or pack up their armies and leave, so why bother? Thus far, the only person to accept was Daenerys who did so for morale reasons. However she made sure to send a former fighting slave as her champion. That way the (slave-trading) city wouldn't gain much face if he lost, but would be humiliated if the champion wiped his ass with their champion. Which is literally what happened.
While Daenerys is besieging Meereen the city sends out a gaudily dressed champion to taunt them. Many of her bodyguards and officers want to fight him but she considers them to be too valuable to waste, so she decides to send Strong Belwas as he's somewhat expendable and losing to a former slave would make it particularly humiliating for the Meerenese.
Although not shown, Ironborn warrior Ser Harras Harlaw takes Grimston castle by challenging any warrior inside to defeat him in single combat. After he defeats seven (a holy number) those besieged surrendered because the Gods had spoken (i.e. their morale was shattered and this was a face-saving way to quit).
In "The Sworn Sword," the water dispute between Ser Eustace and the Red Widow is resolved by a combat by champion. Dunk fights for Eustace and Ser Lucas fights for Lady Rohanne.
The Aeneid ends with a such a battle between Aeneas and Turnus, though not quite so useful as this happened long after months of deadly combat.
Jim Butcher's The Dresden Files novel Death Masks opens with Ortega challenging Dresden to such a combat, intended to be determined by matching wills. Ortega cheats during the subsequent battle in a very extreme manner, and manages to escape. Fortunately, he doesn't escape Ebenezar McCoy and his Soviet satellites.
In a later book, Harry and Ramirez challenge two White Court vampires in a much less restricted battle. And again, the vampire cheats when it starts to go against him.
And in Changes The Erl-King decides this is a good way to determine which of his guests is going to be ripped apart. The two powerful vampires end up nominating their blood beast creature and a random Mook who got killed within the first ten seconds against Harry and Susan. Given that when it lost they got ripped to shreds by goblins maybe one of them should have stepped up.
And again in Changes, the Red King declares Harry and Arianna Ortega's dispute will be resolved through a duel. Harry wipes the floor with Arianna but, once again, the vampire cheats.
In Cry of the Icemark, a general on the villains' side challenges the heroes' queen to single combat to decide the war between their lands. The deal is that if he wins, she surrenders Icemark, and if she wins, he leaves. Though Thirrin realizes and notes that this would only keep them away until a new general comes along, they do battle anyway.
In The Right Stuff, Tom Wolfe characterizes the "Space Race" between the USA and USSR as a form of single combat. Because the possibility of all-out war was distateful and frightening to both sides, they channeled their rivalry into a race to the Moon.
The whole Southern Judicial system in the One Rose Trilogy is based on this trope
In New Jedi Order, Corran Horn challenges Shedao Shai to single combat over the fate of Ithor. Corran wins, but the Vong still decide to devestate Ithor.
Mentioned but averted in two books of the X-Wing Series. In The Krytos Trap, Wedge accepts a challenge to a ritualistic knife duel with Tal'dira, which Wedge, as a short pilot, knew he would likely have trouble with. It turns out to be merely a test of Wedge's resolve (and that of the merchant who was attempting to deal with Wedge), and the challenge is nullified soon after. In Starfighter of Adumar, Wedge reflects that he'd be fine with flying against and killing a champion, be he Imperial or Adumari, to decide the planet's allegiance, but instead he's expected to fly against bad Adumari pilots and kill them for "honor", which is weighed against how the Imperials do.
"Bad Cartannese pilots" is right. No formation discipline, almost no simulated-weapons drills or flight simulators, and a "combat equals honor" mentality that leads to top pilots dying in droves. Not all of the Adumari are poor pilots (although not up to galactic standards by any means), but the Cartannese were truly duel-happy maniacs.
In Splinter of the Mind's Eye, Luke ends up having to fight a native Coway champion to win the freedom of his allies and his own right to walk out of their major encampment again.
In Andy Hoare's White Scars novel Hunt for Voldorius, Jhogai demands the right, as company champion, to face off against the Chaos champion Nullus. He loses.
In Matthew Arnold's reworking of the old Persian epic of Sobrah and Rustem, a father and son find themselves in two different armies and end up in a Combat by Champion. Interestingly this was one of C. S. Lewis s favorite poems, as much for the descriptive power as for the plot itself.
In book 26 of Animorphs, the Animorphs are pitted against seven Howlers to decide the fate of an entire alien planet.
Despite being set in an age where the clash of massed armies have replaced single combat, Belisarius Series has two notable cases of single combats.
The Backstory has one between Rana Sanga and Raghunath Rao that made them both famous.
Then Rana Sanga (again) and Valentinian has one in part 4, Fortune's Stroke as well, lasting for an entire chapter, though most of it explores the symbology and psychology of the fight. The duel is also supposed to be a diversion so that Belisarius's army can retreat while the Rajputs are occupied with the fight. The Rajputs know this but their society is based on Honor Before Reason so they to watch the fight and do not interfere. It is clear that the duel will be the stuff of legends and all of them want to be there to witness it.
E. R. Eddison's The Worm Ouroboros has the wrestling match between Lord Goldry Bluszco of Demonland and King Gorice XI of Witchland, with Witchland's claim for suzerainty over Demonland at stake.
The Elven high king Fingolfin challenges the Dark Lord Morgoth to single combat in The Silmarillion. Unfortunately, Fingolfin loses, but it's so epic Morgoth is afraid to face him in the first place. And Fingolfin manages to wound Morgoth seven times before dying, and with his dying breath gives Morgoth a permanent limp. For the rest of the war until the coming of Valar, Morgoth would not come out of his fortress for fear of ending up in that situation again.
In the Warrior CatsExpanded Universe novel Crookedstar's Promise, one of the battles for Sunningrocks is decided by a duel between Mudfur and Adderfang.
In Sean McMullen's Greatwinter Trilogy, 40th century North American society has a long and storied tradition of conducting all warfare by chivalrous Old School Dogfights with aircraft built of cloth and wood and flown by a pilot-aristocracy. Fighting a war on the ground with commoner infantry is considered dishonorable and unchivalrous, and a massive waste of scant resources, until infiltrators from another continent reintroduce the concept of total war.
Averted in The Painter Knight. A child ruler escapes her Evil Uncle, and reaches the safety of a loyal cousin, who raises an army to bring the traitor to justice. Before the climactic battle the uncle challenges the cousin. Her sovereign forbids it on the grounds that her uncle is "not to get outta this by dying nobly."
A main plot point in The Prize in the Game by Jo Walton. When Oriel is about to be invaded without war by an overwhelming force, the invaders are manipulated into only doing combat by champion. Oriel's champions Darag and Atha fought several single combats daily to hold of the invaders for over a month.
In David Gemmell's Drenai series, champions dueling are a traditional part of sieges. However, they tend to occur toward the end of the siege when city or defensive position is close to falling. If the defenders' champion loses, they can surrender without losing honor. If the attackers' champion loses, the defenders are traditionally provided with supplies and the attackers continue the siege. No one expects the attacker to abandom a successful siege just because of the outcome of a single duel.
Gesta Danorum: Fighting against the Swedish usurper Sorli, Ragnar and his three sons Bjorn, Fridleif and Radbard take on a Swedish champion and his seven sons in a public single combat.
In Pact, as part of his attempts to avoid being enslaved by the Incarnation of Conquest that rules Toronto, Blake Thorburn challenges him to a contest where they each select five champions, surrender all their power for the duration, and let the champions fight, with whoever surrenders or is killed by the opposing champions being the victor. Being an Incarnation of a concept, Conquest cannot die unless the idea of conquest does, and surrender is in fact impossible for him, so he naturally accepts-only for Blake's champion Rose to trap him within a binding circle, leaving him powerless and the contest prolonged indefinitely, Blake having been more than willing to give up his ability to use magic in order to keep Conquest imprisoned.
Live Action TV
Doctor Who "The Christmas Invasion"; a newly regenerated Doctor saves the world by beating the leader of the Sycorax to ritual combat, standing as Earth's champion. During the course of this fight, the Doctor loses and regrows his right hand. When the leader tries to go back on it, though? The Doctor kills him easily. With a satsuma. At Christmas. Having just woken from a coma and getting his hand cut off.
"No second chances. I'm that sort of a man."
The Aeneid ends with such a duel between Turnus and Aeneas, though it isn't quite as useful as the sides have already endured long months of war.
In Wolf of the Plains, right after the Tartars are defeated, Temujin and Eeluk fight for who will be khan of the Wolves. Temujin wins.
In an episode of Deadwood, Heart and Swearengen's duel for control of the camp turns into a Combat by Champion, as each man sends his dragon to fight the other's in the street. The fight doesn't settle anything, but it does rattle and weaken the loser.
Angel. In one episode, Angel kills a demon who turns out to be a pregnant girl's champion who was going to fight in her name against a demonic tribunal. Naturally, Angel takes his place and fights for her.
Merlin: In one season 4 episode, Arthur avoids all out war by battling the other kingdom's champion and winning
After being captured, Jaime Lannister suggests this to Robb Stark as a way of resolving the brewing civil war. Robb declines, knowing that he'd lose against a member of the Kingsguard.
When Dany besieges Meereen, the Meereen Masters send a champion to insult her and challenge her to single combat. She sends Daario as her champion (Strong Belwas is Adapted Out). While everyone knows that the fight will not decide the battle, the side that loses will be demoralized. Daario wins in a Curbstomp Battle that lasts a few seconds. The actual impact of the fight is that it convinces the slaves of Meereen that with Dany's help they can rebel and gain their freedom.
In one episode of Xena: Warrior Princess, Xena manages to save a bunch of soldiers from being annihilated by the barbaric Horde when she stops seeing them as monsters and learns that they respect Combat by Champion. She fights and defeats their strongest warrior, and the Horde departs.
Wonder Woman: "Wonder Woman’s Return": After being in a stalemate with Dr. Solano, he proposes to Wonder Woman a sword fight. "Winner gets all." It’s a trap.
In a Greek legend, two brothers agree to rule the throne of Thebes on alternating years. After the first year, the first brother Eteocles predictably refuses to step down from the throne. His brother, Polyneices, gathers a large army to take the city by force. The two sides fail to defeat each other, so they make the brothers duel to decide the war. Similarly to the above example, the duel decides nothing. It's for a totally different reason, though: they kill each other in the end.
David and Goliath from The Bible. After David wins, the Philistines flee and the Israelites slaughter them.
Eric Bischoff once thought of settling the Monday Night Wars of the '90s between WCW and then-WWF in this manner. Not with the WCW champion vs. the WWF champion, mind you, but with Bischoff vs. Vince McMahon. Vince, knowing that it was a publicity stunt and nothing else, agreed to the match on the condition that it would not be at the next WCW pay-per-view (as Bischoff wanted), but that it would be in an empty parking lot devoid of cameras. Bischoff ignored this, and when the pay-per-view rolled around, the "match" took place, with Bischoff being declared the winner via no-show.
In Warhammer 40,000, it's an ancient tradition that whenever a Dark Angels company and a Space Wolves company meet, each selects a champion to fight in a (usually non-lethal) duel, in honour of the battle between their Primarchs, Lion El'Johnson and Leman Russ.
In Warhammer, meanwhile, units with special characters can have them challenge opposing units's special characters. If they win, the chance of the opposing side breaking off and fleeing shoots way up. The Warriors of Chaos have to make a challenge if they can, because their reason for fighting is to impress their gods - doing so is much easier by hacking down lords and masters instead of Mooks.
And even if they didn't have to, they probably would anyway unless really, really seriously outclassed, because they get special bonuses for shredding enemy leaders in single combat - besides the obvious benefit of scaring the crap out of the other side, who watch trembling as the psychopath in the horned helmet brutally eviscerates their leader.
Bretonnians from Warhammer Fantasy are a very special example of this trope. Since they are knights in shiny armor, they are expected to meet their enemy in duel. Latest armybook gives them Virtue that forces them to challenge and an magic item that forces enemies to accept challenges. Combine them and you have a knight who never lives to kill other heroes.
Dark Sun is quite low on resources, so 'combat by champions' is one of traditional ways to settle dispute in the desert.
In the Magic: The Gathering set Shards of Alara, the world of Bant has an entire culture founded on this very trope. The game mechanics reflect this with the keyword ability "Exalted", which gives power boosts to any creature that attacks alone.
The card Dueling Grounds imposes this by allowing only one creature to attack and block each turn.
The Archenemy scheme Choose Your Champion also fits as well.
Many roleplaying games resolve mass combats this way, using a small sample of both sides' forces to decide the outcome of the entire battle. A few games offer more realistic mass combat systems, but even then this trope often ends up invoked due to Rule of Fun.
The Clans in BattleTech have built an entire system and protocol revolving around Combat by Champion. Opposing factions will "bid" down their forces to the minimum practical amount, selecting a few of their best warriors who meet in a proxy battlefield called the "Circle of Equals". Pretty much every big dispute in Clan life is ultimately solved by a few champions killing each other to decide who's right. These battles are known as Trials, with various types. Trials of Position have Clan warriors fighting for rank, Trials of Possession have Clans fighting for a place or resource, Trials of Refusal have one Clan disputing the actions of another, etc. During the early months of their invasion of the Inner Sphere, they even try this with Inner Sphere forces. The IS factions, not being Proud Warrior Race Guys like the Clans, of course lie about what the number and disposition of their forces. Hilarity Ensues. ComStar was an exception, as they won the Trial of Possession for Earth against the Clans fair and square, but otherwise the Inner Sphere took full advantage of the Clans' honor and naivety at every turn.
In The Golden Apple, the adaptational equivalent of The Trojan War culminates with Hector arranging a prizefight between Menelaus and Paris. Ulysses accidentally KO's Menelaus while coaching him, takes his spot in the ring and knocks Paris out.
The tribes in BIONICLE's Bara Manga setting have agreed to settle disputes this way to save resources. As a result, these Gladiator Games have become a Matter of Life and Death. Subverted when a new tribe joins the system and raises an army anyway.
Part of the back story of Suikoden II involves a duel between the champion of Highland (who is Riou and Nanami's adopted grandfather) and the champion of the City States of Jowston, to end the long war between the two nations. Which turns out to be just one of many temporary ceasefires between them.
Routinely done in the Suikoden series, through the Duel system.
In Suikoden V, who the Crown Princess of Falena marries is determined by a tournament. Generally, the nobles don't fight themselves, sending champions or other representatives in their place. The current queen's husband, Ferid, shook things up by representing himself and winning; during the game's early Inevitable Tournament, Belcoot hopes to do the same.
The first Heavy Gear video game has the player partake on a one-on-one fight against a single enemy Gear to settle a final standoff between two enemy landships, both immobilized and forced to either pound each other into submission with their guns or settle this "with honor."
In the Romance of the Three Kingdoms video games by Koei, an officer in battle may attack by challenging an enemy officer to a duel. The winning officer usually captures the loser, with the loser's unit routing with their commander gone. Usually it's damn near impossible to get the computer to duel unless it believes it will obviously win or else has no chance to win in continued combat. Usually, declining to duel damages morale.
Similar duels also take place in Dynasty Warriors, which is based on Romance of the Three Kingdoms, but annoyingly only at the computer's discretion. Players cannot initiate them. The computer is more willing to initiate them in this series, however. Declining still hurts player morale.
In Baldur's Gate II: Throne of Bhaal, whilst merrily invading Sendai's Enclave, the player gets the option to face the captain of a Drow war-party in single combat. The catch: the Beholder enforcing the duel casts a Geas spell on both groups, so that whichever champion that fails causes their entire party to die instantly. The Beholder himself, who is on the side of the Drow, does not die, having had the good sense not to include himself in the spell. Then you chat with him for a while. He's really quite pleasant.
In Fire Emblem: Radiant Dawn, the Begnion general Zelgius challenges Laguz Alliance general Skrimir to a duel. Skrimir's acceptance was stupid, because Not only were Zelgius' abilities superior, but Skrimir was ordered not to move until he was given a signal. His loss, destroys Soren's plan and forces the Laguz to do a full-scale retreat. And they were doing so well, too.
The intro to Heroes Chronicles shows the barbarian leader Tarnum being killed in a duel with King Rion Gryphonheart, while their armies watch. Tarnum gets better.
Essentially the plot of League of Legends. The league was formed as a formalized, five a side version of this trope to avoid another world destroying magic war. Many nations in the games world are joining so they can avoid losing a war against Noxus, only for Noxus to beat them in the league and take over anyway.
Indie Turn based strategy title Solium Infernum has this as an option when you declare war.
In Dragon Age: Origins, it's possible to settle the Landsmeet with a duel between Loghain and you or one of your party members. With a certain exception...
Arl Eamon: "Ah, Warden... No. I'm afraid we can't leave the fate of all Ferelden up to your dog. Anyone with a leftover ham bone could buy his allegiance. Choose someone else."
Earlier in the game, there's also a knight who demands a duel with the main character. If he dies his friends will accept the outcome and leave quietly. They will only attack if you break the rules and send your other party members to fight as well.
The example in Dragon Age II would fit this, if not for the fact that to get to the Qunari leader you have to carve your way through his forces first through the entire city. Once you get to him, you may still have to fight a few more of his grunts to fully earn his respect. You then can either fight the Arishok and his guards (with your entire squad) or just you and the Arishok. Fittingly, after this fight, you are henceforth known as the Champion of Kirkwall.
Supposedly, this was one use of Deathwatch in the backstory of MadWorld. Agent XIII wants to end Deathwatch because it's degenerated into a Blood Sport.
In Sid Meier’s Pirates!, there are many swordfights, against captains of ships/armies. Regardless, once you beat the captain in a swordfight his entire crew/army surrenders. (Also inverted to a degree, at least in the most recent remake: If you're the last member of the crew standing, you'd better be capable of pulling off a flawless victory, or else you'll be forced to surrender the next time you get hit.)
Played straight then subverted in the intro to Total War: Shogun 2, where the general of an army besieging a castle sends a champion to fight the champion of the defenders. The duel is played out beautifully, as both imagine they're fighting in a garden surrounded by cherry blossoms (they're really fighting in snow). The champion of the attacking side wins and walks back triumphantly, only to end up with a dozen arrows in his back. The infuriated general orders his forces to attack.
It's revealed in the backstory to Star Wars: Knights of the Old Republic that the Mandalorian Wars ended shortly after Revan killed Mandalore the Ultimate in single combat. While normally this would result in a very short interregnum period, while they chose a new Mandalore, Revan took Mandalore's mask and hid it on a remote planet. Without this symbol of power, the Mandalorians couldn't choose a new leader, and the war quickly came to an end. The novel Star Wars: The Old Republic: Revan reveals where Revan hid the mask (it was in the tomb of the Sith Emperor's half-brother).
Centurion: Defender of Rome has fleet battles represented by the two flagships fighting. The trope is subverted, since winning the flagship battle can still cause the rest of your ships to be destroyed.
In the old DOS Dungeons & Dragons game Pool Of Radiance, the party is ordered to deal with a lizardman colony that is threatening Phlan. While it's entirely possible to eradicate the lizardmen altogether, you can also resolve the matter by settling an internal conflict between the elderly (and relatively peaceful) chieftain of the tribe and a younger insurgent who's the main reason why Phlan wants the lizardmen dealt with in the first place (and he's also taking orders from the game's Big Bad). The conflict is settled in this trope's manner. The chieftain is too old to fight, so he's allowed to select a champion to fight in his place (read: one of your party).
In Spacetrawler, Emily realizes that her side is outgunned in a space dogfight. She contacts the leader of the opposing side, Kuu-drahc, and goads him into agreeing to call off the space battle so the two of them can fight, hand-to-hand, on the planet below.
Redcloak and a master cleric have one of these in The Order of the Stick, as Redcloak's armies are overrunning Azure City. Redcloak explicitly takes the offer for no other reason than to prevent his troops from being needlessly slaughtered (as he is currently winning the battle), and subverts protocol by killing all the human bystanders afterwards anyway. Granted, knowing the Azurites, they probably would have done the same thing to his goblin troops as well.
In The Gamers Alliance, CaptainIsmail of the Black Guard and DreadlordLeraje of the Northern Horde fight a duel to the death to determine the fate of the city of Vanna: if Ismail wins, the demons will retreat. However, the horde has no intentions of keeping the bargain so no matter which way the duel ends, they will invade Vanna. The heroes suspect as much so they use the duel as a means to distract and stall the demons long enough to free the demons' captives and hopefully catch the horde by surprise and perhaps assassinate a few of the demon commanders while they're at it.
In Ben 10: Alien Force, this isn't just a battle of honor, it's intergalactic law when it comes to invading armies that their two strongest warriors can fight to decide the winner, which Vilgax uses to conquer 10 worlds.
Samurai Jack had Jack in a battle with Aku to settle things once and for all, but Jack couldn't use his sword and Aku had to be human and not use his powers. Aku cheated right from the start. Too bad that Jack expected it...
In one episode of The Transformers, Megatron proposes an honor duel between himself and Optimus Prime, with both sides to be bound by the results. Megs proceeds to cheat; hands up all who are surprised by this shocking twist.
The 1380 CE Battle of Kulikovo Pol'e ("the field of snipes") was opened by the Russian and Mongol armies each putting forth a champion before the battle, probably in hopes of inspiring the winner's side. The Mongols sent Temir-murza, while the Russians sent the Warrior MonkAlexander Peresvet. Both champions died in the fight, and the battle proper took place thereafter.
In the 624 CE Battle of al-Badr, the Muslim and Meccan armies each sent out three champions before the battle. The battle was still fought, after two Muslim victories and one Mutual Kill, but the result demoralized the Meccan army.
Notably averted between Romans Octavian (aka Augustus) Caesar and Mark Antony. After Octavian's navy defeated Antony's at Actium, Antony holed up in the palace at Alexandria. He sent a messenger out to Octavian, challenging him to single combat to resolve the matter. Octavian was an excellent general, but no match for Mark Antony physically, so he had no reason to accept.
The trope was common for a Roman soldier, at least early in the Republic's history. The Horatii vs the Curiatii (3 on 3), and the original Torquatus and Corvus/Corvinus were famous examples. And there was the idea of the spolia opima or Spoils of Honour, an enemy commander's armour taken from him in single combat by a Roman commander. Romulus was one of only three or four to ever take them.
Bertolt Brecht wrote a play, Die Horatier und die Curiatier based on the Roman story (or myth), although here the three champions on each side represent three armies, in the way a general would represent his troops as well in Peking Opera.
One notable subversion was during the War of the Sicilian Vespers when one monarch challenged another and was refused. No one expected it to be accepted and it was really a propaganda move.
What sometimes happened in several wars was that aristocrats from either side would challenge each other, not to decide the battle, but simply because they were bored! As one of the most unspoken but most present hardships of war is simply tedium (and the nervousness and physical discomfort that goes with it), one can see why a trained warrior might actually prefer fighting.
There were several incidents of this between British and French cavalry pickets during the Napoleonic Wars.
The former vice-president of Iraq, Taha Yassin Ramadan, once suggested that Saddam Hussein challenge George W. Bush to this.
In 545 BC, The Spartans and their arch rivals the Argives both sent exactly 300 of their best men for a battle. The battle ended with two surviving Argives and only one remaining Spartan. The Argives considered themselves victors because they had more men left alive while the Spartans felt they had won because their man had stayed put while the two Argives had run off to tell about their victory. Since neither side was willing to concede defeat a conventional battle was needed to settle matters which the Spartans won.
The Catechism of the Catholic Church orders the excommunication of anyone willingly involved in a duel UNLESS it falls under this trope.
Largely subverted by the Mongols. The Mongols were the most highly organized and disciplined warriors for their time. During the Mongol invasions of Europe and Japan (both highly devoted to individual combat), the other side would oftentimes send out champions, as per custom. The Mongols would usually greet them with a shower of armor-piercing arrows. As the Japanese poem Hachiman Gudōkun states:
“ According to our manner of fighting we must first call out by name someone from the enemy ranks, and then attack in single combat. But the Mongols took no notice at all of such conventions. They rushed forward all together in a mass, grappling with any individuals they could catch and killing them."
Up until the Mongol turned up, this was the standard way of battle in Japan: combatants would not only declare their names and their desire to duel, they'd recite large amounts of their family history as well.
Markus Persson, creator of Minecraft, combined this with Trial by Combat when he proposed to settle a copyright dispute between his own company Mojang and rival company Bethesda over whether the former is allowed to make a game by the name of Scrolls... by means of a Quake match between each company's three best players. Alas, Bethesda rejected it.
At the battle of Vouille in 507 AD, Clovis, King of the Franks, (aka Chlodovech) faced Alaric II, the young King of the Visigoths. In dispute was an area on what is now the French side of the Pyrenees. Clovis had superior forces and could have crushed the Visigoths (but lost a lot of men, and battles are never actually certain) but instead, he offered single combat to Alaric, who took it. Clovis won.
In A History of Warfare John Keegan records observations of primitive tribes who would settle quarrels by assembling at a ceremonial place where the young men would shoot at each other with bows and the elders would watch, ready to intervene if it got too bloody.