Essential to the Twist Ending of "Endless Odyssesy": Harlock promises early into the series that he will help Tadashi Daiba succeed in his vow to kill the man who murdered his father, commenting on his belief that a man cannot break a promise and anyone who would break a promise or an oath is not a man. After Nu is defeated, he then reveals that he was the one who killed Daiba's father, as he had promised to do so if Tsuyoshi Daiba gave in to his hunger for knowledge and betrayed humanity to Nu. He repeats what Tsuyoshi's spirit had earlier revealed to Tadashi, that he has vowed to Tsuyoshi to kill Tadashi if he cannot become a man, and firmly declares that Tadashi either kill him or be shot down.
Inuyasha will not run or hide from a fight, even if caught in his powerless human form. The anime expands this to explore how Inuyasha and Kikyou first met. When Kikyou demands to know why he didn't attack her when she was too injured to fight back, he explains he doesn't play dirty.
Sesshoumaru will fight his opponents head on, even when severely de-powered. He inflicts a Die or Fly test on Inuyasha to prove Inuyasha's ready for Meidou Zangetsuha, promising he'll give up both swords if it works. Badly injured, Inuyasha succeeds, Sesshoumaru keeps his promise, and Naraku ambushes Inuyasha with Tenseiga. Sesshoumaru dives into the meidou to save Inuyasha, destroying Tenseiga and also his ability to escape the meidou. When Inuyasha notices, Sesshoumaru says saving them is up to Inuyasha now, prompting Inuyasha to realise he's been given Meidou Zangetsuha.
In Speed Grapher, Saiga relentlessly protects Kagura from Suitengu and the members of the secret underground club of the rich and elite of Japan, against the advice and protests of his friends Ginza and Bob, who believe throughout the series that he should simply leave her to her fate. Saiga is willing to die in order to allow Kagura a chance of happiness, and in the end goes blind while saving her.
The heroes of Rurouni Kenshin follow this trope to a tee. Surprisingly enough, even the heartless Social Darwinist villain Shishio Makoto follows this trope, threatening to kill his scheming right-hand man, Houji, who proposed a cowardly assault on the loved ones of the heroes while they dueled his lord; for such behavior is, to quote Shishio himself, "Against the Way of the Warrior." They then do it anyway after Shishio lies to the Juppongatana about a supposed infraction Houji had committed that had put them in danger, as a way to put Houji on the spot and force him to prove the strength of his devotion, with Houji's resultant display of loyalty and committment impressing Shishio sufficiently that he claims the idea as his own.
Son Goku's seemingly illogical and insane unconditional love for life and his ability to forgive anyone has allowed him to turn the dozens of monsters, madmen, and murderers that he has fought throughout the Dragon Ball Z saga (with the unfortunate exception of Frieza, Dr. Gero and Cell) into heroes.
Another infamous example is when Goku gives Cell a Senzu bean to fully heal himself so that he can fight Goku's son Gohan at full strength. He was confident in his son's strength and he is partially impaired by his Saiyan genes. What he did to Frieza on the other hand...
The entirety of the Cell Games only goes down the way it does because the heroes treat it like a real tournament. Instead of simply powering up to full and the entire group all blasting Cell into oblivion at the same time, Goku goes in first, exhausts himself, then has Gohan go in, resulting in the entire group being beaten to near death. By the time the group wises up and actually DOES do this Cell has powered up so much and eliminated or weakened several of the Z Fighters so that those who are left to fight are too weak to do any actual damage. This is particularly odd because Cell would not be the first villain nor the last where ganging up upon them rather than giving them a "fair fight" is the exactly what they attempt to do.
The whole scene near the end of the Buu arc where Goku is refusing to throw the Genki Dama because Vegeta's in the way must qualify for this. He's holding back an attack with enough power to destroy the final Big Bad because it would kill Vegeta too. Forget that not throwing the attack would doom the entire universe including that one person he's trying to spare.
While generally a Combat Pragmatist, Future Trunks falls into this at least once during the Cell Saga. After Cell becomes perfect, Trunks deliberately stands back and watches while Vegeta is getting his ass kicked because he knows Vegeta is too prideful to want his help, despite Krillin literally begging him to do something, as well as the fact that Vegeta's pride is exactly why Cell was able to become perfect in the first place. He only steps in to fight after Vegeta is beaten unconscious.
In the sequel series he takes this to ridiculous levels, allowing himself to be defeated losing his mecha and seriously risking his own death rather than allow his side to wipe out an enemy force instead they try to outrun and only disable and shoot near misses. He also refuses to hold a grudge and kill enemy pilot Shinn Asuka when the guy has nearly killed him and killed countless pilots on his side and it's clear the man as a very nasty vendetta against him.
Played equally straight, previously, with Shiro Amada of Mobile Suit Gundam: The 08th MS Team, who believed in killing only as an absolute last resort, despite being the commander of a mobile suit unit.
And the fact that Zeon gassed his home colony in front of him during the first week of the gas doesn't change his mind about this. They're a reason why people laughed in his face when talking about this.
Both these instances can be traced back to Judau Ashta from Gundam ZZ who began acting like this about the same time they touched down on Earth and the show started Growing the Beard, simply because he couldn't handle any more death. Sometimes it actually worked, such as with Masai and Puru 2. However, it usually failed miserably (the death of the entire Blue Team, Rommel, Chara Soon, and Haman). At the end of the series, having born witness to the Federation dragging its heels before mobilizing a fleet to defeat Neo Zeon and showing up after the battle was over, he was at the breaking point. To let him blow off steam, Bright let Judau deck him in the face... something awesome for both of them.
Then there's Char Aznable in Mobile Suit Gundam: Char's Counterattack, who purposefully leaked the specs for the cutting-edge Psycoframe system, knowing that Amuro would get it and have it built into his next Gundam. The reason he did this was because he thought there would be no point in defeating Amuro if he and Amuro weren't evenly-matched in the battle.
In Gundam Wing, Wufei tracks down Treize Khushrenada in an attempt to kill him to prevent him from taking control of the Earth Sphere Alliance. However, instead of blowing Treize to smithereens with his Gundam, Wufei accepts a challenge to a sword duel from Treize which he loses. Treize reciprocates Wufei's earlier gesture of honor and allows him to leave in his Gundam rather than seizing the state-of-the-art machine for study or reverse-engineering. Wufei departs—again passing up the perfectly good chance to eliminate the would-be dictator with superior firepower.
Played as a major defining character trait for Zechs Merquise. He won't defeat an opponent if it not a fair fight. This translates to, he can disarm them in mid-combat, then spare them because they are no longer armed with a weapon. His need to be honorable certainly seems to cloud any sense of priority, as he will give his rival a powerful and destructive Gundam, just so they can have a fair duel, while in the middle of a war.
In Endless Waltz, Zechs, Noin, and the Wing boys also do this. After they defeat hundreds of enemy mobile suits without killing a single soldier, Quatre comments that if they were fighting to kill, they could have blown through the Mariemeia Army far more easily, but then there would have been no point to their intervention.
In Gundam 00, Graham Aker is the embodiment of this trope. "Sounds reasonable! Too bad I'm an unreasonable man!!!".
Especially pronounced in the second season where he and Setsuna are duelling over an ocean. Setsuna's Gundam malfunctions in the middle of the fight and Graham leaves him be because he can't see any value in defeating a disabled opponent.
In Hayate the Combat Butler, the titular character's suicidal devotion to Nagi and every person that needs his help often falls into this. Plus, the fact he never called social services on his deadbeat parents (who are either heartless, brainless, or both) as a child speaks volumes about his kind character.
Becomes downplayed though the course of the series due to how cynical he has become thanks to his horrid childhood.
Ranma ˝ would be considerably less funny without this. It also would've been much much shorter.
This can actually be considered an element of Ranma's fighting style; whenever challenged to one of the various Martial Arts and Crafts, he always has to Beat Them at Their Own Game, even if he has only a minimum amount of time to pick up the rules and despite the fact he's usually going against a champion of that style. During the Martial Arts Dining arc; despite the fact Ranma is clearly starving, s/he insists that s/he will only eat what s/he earns from the table/arena. In the anime, at least, s/he even goes so far as to turn down Akane when she offers her fiancé some smuggled food. This almost results in Ranma losing the contest when his/her frantic efforts at both fighting and thinking up counters burn out what little energy s/he has left.
Nodoka Saotome and her Seppuku pledge is a rather darkly humorous take on this, seeing as how the so-called "pledge" is ambiguous as all hell (It was that Ranma would grow up to be 'manly'). While the series' heavy reliance on Rule of Funny ultimately leaves the audience too skeptical to believe the threat would ever REALLY be carried out, all the evidence in the series is that, if Ranma thought he had sufficiently disappointed his mother, he would go through with it. This is despite the fact that Ranma was about a year old when he 'agreed' to it.
One thing that often gets over looked is that Ranma's father Genma, despite being a Dirty Coward, has come up with two super-powered techniques which he never uses simply because he vowed not to. He holds to this even when he's getting beaten senseless and could easily wipe the floor with his attacker if he broke them out. He'd also submit to the Seppuku thing if he was called on it (of course, in typical Genma fashion, the trick is arranging matters so that he never does actually get called on it). Honour is a finely tuned thing.
The only way to cure Kibagami Jubei, the hero of the anime classic Ninja Scroll, of the slow-acting poison in his body was to take a Girl Ninja whose own body's potent poison would destroy the comparatively weaker venom in the process. But knowing that this would obliterate what little was left of her sense of self-worth, already shredded by the fact no man dares to touch her, Jubei instead refused her offer and walked off like a gentleman, into certain death.
Negi Springfield of Mahou Sensei Negima!!, in spite of being a talented young warrior, is so kind-hearted he even offered mercy to a Demon Lord who destroyed his village and crippled his cousin. His kindness and merciful nature has almost cost him his life on more than one occasion.
He tends to show mercy when he perceives an unvoiced If I Wanted You Dead... subtext — he's just painfully ready to see those. He also benefits more from showing mercy than he would from finishing enemies of the week off. For example, the Demon Lord (who was just a summoned lackey anyway) dropped on its way back home the second hint so far that the village massacre did no truly permanent harm to anybody... except emotionally, if Negi let it...
In Super Dimension Fortress Macross/Robotech Millia insists that Max shoot to disable Zentradi battlepods to simply put them out of action instead of killing them to show that the Terrans are serious about wanting peace. Even though this could be seen as completely insane considering the Zentradi finally decided to fight full out to destroy the Macross, Hikaru Ichijo learns what his wingmates are doing and joins this act of mercy along with other human pilots despite the dire situation. As it turns out, this gesture actually saves the ship because many of the Zentrani forces, already becoming enthralled with Terran culture, learn about the humans' mercy and decide to mutiny throughout the fleet to stop the fight. Commander Breetai is horrified at the unprecedented insubordination and is forced to order an immediate ceasefire in direct violation of his orders.
Prior to a certain event near the end of the first series (Euphie's death), Suzaku follows this trope pretty closely despite working for the evil empire. He refuses to shoot his friend even when threatened with being shot himself if he doesn't, he stops pursuing his target in order to save endangered civilians, he always gives his targets a chance to surrender (even after things get pesonal), and basically has to live as a Technical Pacifist who's involved in killing tons of people. He also regularly risks himself to save others (although this is partially because he's a Death Seeker).
Lelouch himself falls under this on one occasion: the chess match against Schneizel. Schneizel deliberately moves his king into check. Instead of accepting an immediate win, and in the process captivity of Suzaku, one of his biggest obstacles, Lelouch refuses the move. Schneizel notes that the Emperor would have immediately checkmated, and has just learned the type of man the still masked Zero is.
Digimon has a few examples:
In Digimon Adventure 02 there are two cases of this: Cody, who suffered an Heroic B.S.O.D. for lying, and for a while considered himself worthless to the point of not being willing to be the one chosen to escape from a underwater base in order to save the others. The D-3 chosen children also showed the troupe when it came to the point of having to kill an actual digimon, which wasn't a problem for the previous chosen.
In Digimon Tamers, this a definite, if not lampshaded, character trait of Ryo Akiyama.
Though she knows she can't do it for everybody (and this fact does cost her quite a bit of her happiness), Mai Tokiha from Mai Hime possesses an unshakable desire to protect her friends and her brother. She even wanted to find it in her heart to forgive a pair of her enemies (who wanted to turn her school into a pile of smoldering rubble), because she saw them happily singing together in a park one day and figured that even they deserved a chance at happiness.
Subverted in (of all shows) Transformers Armada. Faced with the choice of leaving his friend, Wheeljack, trapped in an inferno and going for help, or staying with him to the end, Hot Shot goes with the former, but is forced to abandon Wheeljack because his commander believed in The Needs of the Many over the principle of No One Gets Left Behind, and refused to risk any more of his troops in the fire. Hot Shot defied his commander and tried to go back for Wheeljack, but by then the flames were too much for him to overcome. The decision is later regretted, out of both reasonable, genuine guilt, and the fact that Wheeljack survived, and did not...take abandonment very well.
Tendō Rushuna in Grenadier specifically fights to "remove an enemy's will to fight" without killing, or if possible, without hurting them at all.
In Vinland Saga it's more of a case of vengeance over reason, with Thorfinn risking life and limb to protect the man he wants to kill.
More importantly is the way he always insists on doing the killing the 'honourable' way, in a one-on-one duel. Said man, who is more experienced, skilled at playing the younger man as a two-cent kazoo and far more Combat Pragmatist(and once was in the same position as Thorfinn; he assassinated his victim in his bed after spending two years worming himself into his graces), considers Thorfinn's methods to be a major case of What an Idiot.
The latter incident is similar to one time in the first season when Nanoha intervened against Lindy's orders to help Fate seal the six Jewel Seeds in the ocean, rather than wait until she was exhausted and vulnerable afterward to capture her, even giving her half the seeds. Thankfully, Fate had not collected enough seeds for her mother to reach Al-Hazard.
Hikaru from Magic Knight Rayearth invokes this directly in the first season during her fight with Lafarga. When Umi implores her to use her magic to save her life, Hikaru replies that "The opponent is a swordsman. I won't use magic either," despite the fact that using her fire magic would have done the job in an instant.
Despite the carnage that inevitably occurs around him, and his superhuman skill with a gun, Vash the Stampede from Trigun is absolutely determined never to kill anyone. This puts him in increasingly tighter positions as the series progresses, until he has to choose between killing a villain with his own gun or allowing his friends to be killed. He shoots. Or maybe the villain forced Vash to shoot him with his mind control powers. It's plausible that he would rather just force Vash to kill him than see Vash maintain his no killing rule (even though it would have caused Vash great suffering from guilt). Vash himself might not even know which happened. Fortunately, Vash is practically the platonic ideal of Improbable Aiming Skills, and even towards the end, there's very little death that could have been resolved by him shooting to kill, unless you count him not killing Knives a long time ago.
Oh no, it was very clear that Vash chose to pull the trigger. That was the whole point of Legato's plot — he only used his powers to keep Vash from saving Meryl and Milly directly, forcing him to choose of his own will to pull the trigger. He could have chosen to let them die, instead he chose to kill Legato. It's fiendishly brilliant.
Chibodee and George in G Gundam both lose their rematch to Domon because they showed their attacks to him beforehand, and he was able to learn moves to counter them.
Sai Saici had a different version of this in his rematch with Domon. Even with his Gundam getting thrashed by Domon, he still kept fighting. It took the intervention of Neo-China's Emperor to prevent Sai Saici's death.
The entire premise of Idolmaster: Xenoglossia is that Japan's government is so committed to honoring its post-WWII disarmament agreements, that when the planet is threatened by asteroids that used to be pieces of the moon, instead of arming itself with ballistic missiles to protect itself like most nations did they go to the ludicrous expense of creating Humongous Mecha which can only be piloted by children who have certain qualities to destroy the rocks instead.
Lampshade Hanging: Both protagonist and antagonist fall victim to this line of thinking in Claymore. An awakened being Ophelia puts all of her vulnerable, human portions at her tail and challenges Claire to cut through the awakened being's body using her dangerous "Flash Sword" technique. As Claire begins the test of mettle, Ophelia thinks to herself, "The fool, she could've just ignored me and aimed right for my tail." Ophelia seems to slightly realize that she too is guilty of honor before reason since she agreed to put all of her vulnerable parts in one easy to target place. As she continues to berate Claire's foolishness, Ophelia thinks to herself, "Wait, who am I talking about?"
In One Piece, Lovable Sex Maniac Sanji is completely unwilling to hit a female for any reason whatsoever. This has very nearly cost him his life on more than one occasion, and he's been called out on it as well. Sanji is fully aware of this, but this rule is so ingrained in him that he can not and will not break it for anything.
Sanji also straight up used this trope when, against the advice from his crewmates, gave food to starving and obviously evil pirates who then immediately attacked him. Sanji then said that he stood by his decision.
Because he starved almost to death as a kid starving is something he literally does not wish on his worst enemy. No exceptions.
Another Sanji example is his fight against Wanze; Despite being the strongest of the three (Franky, Usopp, and him), he opts to fight the relatively-weak Wanze due to his honor as a cook even though there are stronger agents ahead.
Also Whitebeard, who'd do truly outrageous and insane things to protect his sons. He is however opposed to rushing in half-cocked, and makes sure to use strategy and not just brute force.
The rest of the crew counts as well, even if it's disobeying their father's wishes. Imagine if they all jumped in to rescue Whitebeard from death?
Nami's adoptive mom, Bellemere, essentially chose to be executed rather than disavow being Nami's mother. On the other hand, the doctor and Genzo point out afterward that their plan to send Nojiko and Nami out to sea to spare them from being discovered wouldn't have worked, as the fishmen had sunk all the boats, and Bellemere, having been a former Marine, knew it would have been impossible to resist the Fishmen, so it's likely Bellemere thought things through more than it seemed.
Interestingly, despite being the main character, Luffy doesn't usually follow this trope to arbitrary levels. You couldn't ask for a truer friend, but he's made it clear that he does what he wants to do, and doesn't care if other people disapprove. He's also willing to break a promise if he gets angry enough.
The mayor of the town Buggy is attacking in the Buggy arc tries to stand up to the pirates, prompting Luffy to punch him out. He later realizes that he was wrong and is grateful to Luffy for stopping him from throwing his life away.
The dueling giants Dorry and Broggy are this Up to Eleven. In short, according to their homeland traditions, if two warriors of Elbaf get into a dispute and neither will yield, they must fight, and the God of Elbaf grants victory to whoever is right. Fast forward 100 years, and these two guys are STILL FIGHTING. What's more, neither of them can remember what caused the argument in the first place; they still fight because its a manner of honor. it was who caught the bigger fish. This is also why Dorry fights even when a bomb goes off in his stomach; he doesn't want to lose face and disgrace Broggy by quitting, and Broggy, even knowing that Dorry isn't at 100%, doesn't want to upset his friend by showing sympathy. Interestingly, even though they're determined to kill each other for petty reasons they can't recall, they're still best friends.
Kid Samurai Momonosuke is too proud to accept food even when he's almost skeletal with hunger which saves him since he didn't eat the addictive, poisonous candy given to the other kids. He finally eats when sees his father give up his own pride.
Smoker would have chosen death over accepting help from a pirate in Hazard Punk if Tashigi hadn't reminded him they had subordinates and little kids to help.
In Fullmetal Alchemist, Edward turns down the opportunity to take the Philosopher's Stone and run, despite it being the one thing he's been searching for for three years. He leaves it, because the doctor who has the stone used it to heal injuries and sicknesses in his town. Edward says that he didn't want to take away the town's life support, and if he achieved his objective at the cost of others, then it would leave a bitter aftertaste. His brother agrees.
Also, even to save his friends, Edward finds himself unable to kill anybody, even his virtually immortal enemies. He makes an exception for Father.
Once the brothers discover the true source of a Philosopher's Stone (human souls), they resolve to never use that means to get their bodies back to normal. And in the end, they didn't have to.
Late in the game, Al concedes to use the Stone during a fight with Kimblee, because he's helping to save humanity, not himself, and the souls in the stone would probably want to fight for what's best for humanity as well.
In the finale, Hohenheim, having exhausted his Philosopher's Stone, was down to his own soul and would likely die soon; he offers it up to save Alphonse, who had sacrificed his bond to his armor to give Edward his arm back and prevent Father from turning him into another Stone. Edward turns it down, because the brothers believed that, as it's their own fault for losing their bodies, they won't have anyone pay for their mistake, even their own father. Probably a good thing, though, because there's a chance that Hohenheim would have ended up stuck in the Gate.
A rare villain example in the form of Kimblee. As despicable as he seems, he still has his code of honor which he never breaks even to save his own life, or at least keep his soul from fading away. Had Kimblee simply stood by as Pride attempted to steal Ed's body when his own was disentegrating, he might have even been able to reassert his own consciousness over Pride's at a later point.
Ichigo believes in fighting his way. He won't let his Hollow get in the way of that, even if disadvantages him to do so. His Hollow taking over allowed him to not only survive Byakuya's killing blow, but to gain the upper hand and badly wound Byakuya. Upon regaining control, Ichigo apologised to Byakuya and asked if they could start the fight over. It was the first time Byakuya realised Ichigo had a lot more honour to him than he'd realised and, fortunately for Ichigo, he agreed.
Ichigo displayed this trait again against Ulquiorra. Ichigo, at the verge of death, was so completely taken over by his Hollow that he lost all reason and not only overwhelmed Ulquiorra with raw power, but even stabbed Uryuu for trying to calm him down. When Ichigo regains control, and sees what he's done to both Ulquiorra and Uryuu, he insists that the only way he'll continue fighting Ulquiorra is if he's given the same injuries in compensation. This means chopping off an arm and a leg. Ulquiorra's too far gone, however, and dies before Ichigo can carry through his vow. It's especially bad because Ulquiorra has very clearly displayed that he can easily regenerate limbs. The fight would be even again if Ichigo just stood by and allowed him to heal up a bit naturally so the offer to have his own limbs cut off is exceptionally irrational.
Ikkaku has vowed to fight and die under Kenpachi's command. To this end he'll even throw a fight to avoid revealing how powerful he really is, just in case the truth puts him under pressure to work towards becoming a captain of another squad. Called out on this by Iba who told him he's not as expendable as he thinks he is, he should be working to get stronger, and he should never put personal pride before his shinigami duty.
Yumichika is so determined to remain a subordinate of both Kenpachi and Ikkaku, and so determined to uphold the squad's kidou-hating, direct combat-loving philosophy, that he hides his power and would prefer to die than reveal the truth in public. Ikkaku may only be hiding bankai, but Yumichika's even hiding his shikai thanks to his power being kidou-based. This means he has to fight his battles on Heroic Resolve alone.
Ukitake placed so much value on honour that he ignored his own misgivings and allowed Kaien to avenge his murdered wife. When Kaien requested Ukitake and Rukia stay out of the fight no matter way, Ukitake agreed and explained to Rukia that there was a difference between a fight for life and a fight for pride. Unfortunately, the culprit wasn't a normal Hollow and had a special ability that proved Kaien's undoing.
Subverted with Kyouraku. He's a devoted Combat Pragmatist and lectures other captains that idealistic fighting is a distraction captains can't afford when in battle. Kyouraku and Ukitake are acknowledged as the greatest partnership in the Gotei 13, and it's made clear that while one side of the partnership plays this trope painfully straight, the other blows it to hell.
Yamamoto lost his left arm in the battle against Aizen. Afterwards, he chooses to leave it as it is, even though Orihime would easily be able to restore it. He says he didn't think it would be right to ask a human for help in a matter that should have only involved shinigami. Yhwach completely mocks him for this attitude, pointing out that if he still had both arms, he might have stood a chance against him, before killing Yamamoto.
Cang Du believes that people with bonds in life should go Together in Death. He'll even go to the trouble of knocking enemies out and dragging them to their comrades so he can kill them at the same time. He also said it didn't feel right to attack Hitsugaya with his own Bankai, even though he doesn't believe Bankai have wills and souls of their own.
2nd Lt.Alice L. Malvin has made it her mission to help people and to repair the damage done to her nation by the recent war. This means that she will not hesitate to call out anyone who she sees as contributing to or aggravating that damage, up to and including The Emperor of her own country, regardless of how capable they might be of physically or politically squashing her like a bug.
Naja of Sands of Destruction is guilty of this on several occasions, most notably when he and Lia escape from a sand submersible working together with the World Destruction Committee. After surfacing and reaching land, he has the chance to arrest them on the spot, but opts to let them go (much to Lia's frustration). After all, they had a deal.
Josuke Higashikata is the poster child of this trope. In a series where Anyone Can Die, he holds the distinction of having not killed a single human, despite the deaths of people around him, including his grandfather early on! Of course, that's just not taking their life...
In the Part 7, Steel Ball Run, Ringo Roadagain is determined to make sure that not only is he aware of everything that could play a role in a duel; he wants his opponent to be likewise aware. There's actually a great reason for this—those duels are to help purify his spirit of uncertainty. If neither side has an advantage (and before you ask, although Mandom's good at saving Ringo's neck, it gives his opponent the same capacity to avoid Ringo's attacks), then he can be sure that his victories were genuinely deserved.
Tenma in Monster, although he distinctly cares about the "right thing" rather than any type of personal honor.
Viral also provides a couple of more straight examples. First he allows Team Gurren to get dressed before a fight. Later he refuses an order to attack Simon because his commander is threatening to kill Yoko if Simon defends himself.
Red from Pokémon Special is subject to this as part of his firm belief that it's not a victory if your opponent is at a disadvantage. This has led to a few minor What an Idiot moments, but even though this series is grittier than the anime, it's still an idealistic shonen, so it rarely bites him in the butt.
Dia also shows shades of this, wanting to stop Team Galactic even though he's just a kid.
Kenichi: The Mightiest Disciple. The series oozes this: even the antagonists, none of whom are even remotely nice people, will abide by the rules of martial arts—which is to say, even though they all want the main character either dead or on their side, none of them will go ahead and kill him, despite having many chances to do so. The title character himself, meanwhile, has a strict set of beliefs that he will not break, regardless of how much sense they make to others. It's completely awesome, of course.
As long as the antagonists from Yami/YOMI are concerned, this is not so much "Honor Before Reason" as much as it is their, as they call it, "pride as martial artists". They want to prove that their way of doing martial arts is the only proper way. If you want to prove that your kung-fu is better, than you have to defeat the enemy by using kung-fu, otherwise you haven't proven anything.
This extends so far that the ones who are defeated will willingly rot in prison once defeated even though it's clearly displayed they can enter and leave at will.
In Hajime no Ippo, World Champion David Eagle is unwilling to exploit Takamuras bleeding wound by targeting it, possibly giving him a TKO win. Any normal boxer would have done so, and Takamura himself does without hestitation. However, this also has to do with Eagle wanting to fight his opponent on the same level, in order to push himself further.
Rock Lee of Naruto nearly destroys his own life to defend his Nindo. Fortunately, there were Healing Hands available.
The whole reason for Naruto trying to help and redeem Sasuke can be summed up as this: he must stand by his word to save his friend, however despicable his friend's actions and motives.
Jin from Samurai Champloo. A running plot-line of the series is the fact that his fellow disciples are trying to avenge the death of their master by killing Jin. Actually Jin's Master was forced to kill Jin during the night by the Big Bad because of Jin's defiance against turning their samurai school into an assassin school/guild. Jin merely killed him in self-defense. If Jin simply told the others this, it would save him a lot of trouble. It would also disgrace the name of their master and school so he takes full blame.
Pokemon Chronicles was a Spin-Off of the original anime where each episode provided A Day in the Limelight moments to many of the show's secondary characters. One episode centred around Ash's friendly rival Richie, who met an older trainer named Silver who dreamed of catching a Moltres. Unfortunately, Team Rocket tried to kidnap the Moltres, and Richie and Silver had to team up to rescue it. They succeeded, but Moltres was injured and exhausted from what Team Rocket did to it. Silver knew he could have captured Moltres easily but he chose to let it go. He wanted to catch Moltres fairly, beating it in an honest fight.
Though in a way, this can qualify as reasonable. Catching a legendary Pokemon in such a weakened state creates the very real possibility of ending up with a Pokemon well beyond your ability to control once its healed, and taking advantage of its moment of weakness sounds like a fantastic way of ruining any goodwill you had just earned from it.
YuYu Hakusho: KazumaKuwabara is pretty much the embodiment of this trope. He loudly declines his teammates' offers to keep him from dying, insisting that men fight their own battles, and later, after whupping a kid who nearly killed him and his Muggle friends, Kuwabara opts to save the kid's life by dragging not only his unconscious body, but the body all three of his friends to a hospital despite sustaining heavy injuries himself.
In the original version of episode 2, Pegasus points out that Yugi could have won at one point. Yugi explains that he couldn't let the match end while his monster was under Pegasus' control. Pegasus calls him a fool.
In the virtual world arc, Ooka/Johnson was caught cheating by Noa/Noah and Jonouchi/Joey would have won by default. However, Jonouchi insisted on finishing the duel. Never mind the fact that a. Jonouchi already had a huge disadvantage (no cards in his hand and no monsters on the field). Not to mention he had plenty of reasons to hate this guy anyway other than the cheating (Ooka was an Amoral Attorney who had admitted he had seen innocent men convicted, and had been insulting Jonouchi the whole time.) Most importantly, they were dueling for their lifes as the loser would be trapped in the virtual world forever. Even Yugi and Anzu/Tea wondered what Jonouchi was thinking.
Johan/Jessie from refuses to use cards that destroy opponent monsters with effects, claiming that such a strategy is too simple and boring.
In the episode where Judai duels Society of Light member Kanda, who uses a game show deck (his cards force the opponent to answer questions correctly or else lose their monsters and take damage). For the final question, Judai remembers that his opponent gave the answer to it earlier that day. The opponent goes Oh Crap!, but Judai purposely fudges the answer, saying he won't answer because it wouldn't be fair, and takes the damage. Sure, Judai wins anyway, but it was still pretty dumb, considering the consequences if he had lost to a member of the Society of Light.
Jack throws Stardust Dragon, which he stole from Yusei two years before, at Yusei and say he can have it back. But Yusei throws it back at him because he wants to win Stardust Dragon back in a duel.
Subverted later, when Yusei is forced to enter the Fortune Cup, since his friends are kidnapped by the organizers, and the only way to save them is reaching the final of the tournament. Jack gives Stardust Dragon back to Yusei, so Yusei wouldn't lose there, and Yusei accepts.
In a partial example, during Yusei's first duel with Aki, he tunes together Junk Warrior and Junk Synchron to summon Stardust Dragon and attacks with it. Rua asked what he was thinking, since Junk Warrior had more ATK points at the time and would have dealt more damage. However, while Yusei did want to win, he also wanted to save Aki from her inner darkness, and knew an attack by Stardust Dragon would resonate with her more.
Crow loans Jack the card Trust Guardian, which has a very useful effect. In his next few duels, when he draws it, he refuses to play it, both because he and Crow got into an argument and because it looks cute, which made it look out of place with the rest of his big, tough, and grotesque monsters. After losing a duel that in hindsight he would have easily won if he had played it, Jack realizes he was being foolish and starts playing it.
In Yu-Gi-Oh! ZEXAL, Mizael, one of the Seven Barian Emperors was big on this. When he and his fellow Barians Vector and Durbe confront Yuma, Shark, and Kaito on the Sargasso battlefield, he refused to use the "Sargasso's Lighthouse" card that his two allies were using (which would have protected him from the Sargasso's detrimental effects) calling it a "coward's card" and preferring a battle against Kaito on truly equal terms.
Reiji uses several cards that inflict damage to himself each turn. In their duel, Yuya is in a position where if he just ends his turn, Reiji will take 4,000 damage and lose, but he hesitates. When he finally does end his turn, Reiji quickly plays a card that mitigates the damage. Yuya says he's glad because it wouldn't have felt right to win that way instead of with his own cards and strategies.
Yuya needs to win four matches in a row to qualify for a tournament. The Maiami City Committee say they are impressed by his earlier matches and offer to let him in right away, but he says it wouldn't be right and does the four matches.
Serena absolutely refuses to back down from a fight, even when hopelessly outnumbered and when Yuya begs her to take the small boy Reira to safety while he holds the mooks off.
Great General of Darkness of Great Mazinger is this. He lives to bring his people to a better life have a battle against Tetsuya, who have become his mutual Worthy Opponent.
Tetsuya mention this in Super Robot Wars Alpha. He mentioned how Great General of Darkness is just a honorable warrior that took the wrong path.
When Mikoto Misaka learns that her clones that she loves like sisters are being slaughtered by Accelerator, she considers the affair her problem and tries to solve it on her own, not telling anybody about it. When she realizes that she can't beat Accelerator, she decides her only option is a Heroic Sacrifice. When Touma Kamijou finds out, he calls her out on being too proud to ask for help and solves the problem by kicking Accelerator's ass.
Touma Kamijou has Chronic Hero Syndrome and absolutely refuses to ignore or abandon anybody in trouble, no matter how injured he is or how powerful the foe. It is later pointed out that he also has a problem with asking others for help, which he later grows out of.
Gunha Sogiita has Super Speed and the ability to teleport, yet he always announces his presence and refuses to ambush or attack from behind. He claims that a true warrior always takes his opponents head-on and does not use dirty tricks. Ironically, this is part of the reason why he sees no reason to learn and improve himself.
Index insists that dealing with enemy mages is her responsibility and not Touma's. She ignores Touma's arguments that he is better suited to fight them.
Leivinia Birdway carries an antique flintlock pistol that only has one shot and takes a long time to load (she typically uses it to finish off a downed opponent). She doesn't use modern guns because of her contempt for science and because flintlock pistols are cooler.
Princess Vilian is an Actual Pacifist, and as a result refuses to learn how to use magic because it can potentially be used to fight.
Eita Touga of 12 Beast frequently advocates running away from the giant, city destroying war-machine. War Leader Jawea and the Harpies choose to stay and fight, to protect their tribe's honour. Less egregious than other examples as fleeing would leave over half the tribe—the elderly, young, and flightless—behind.
In Voltes V, The Dragon continues to fight the Voltes team in the last episode, even though it is obvious his side is about to lose. The only reason for doing so is that he is a noble.
In Lord Marksman And Vanadis, the entire nation of Brune will only fight with swords and thinks that people who use bows are sissies and thus have no honor. The protagonist (an improbably skilled archer) politely thinks they're idiots.
That's not the best example in the series though, oh no. The best example is the protagonist's Childhood Friend and Meido (of the non-battle variety) staying in the protagonist's mansion when an invading army ransacks the town, only starting to flee when the enemy general enters the mansion and announces his intention to rape her. Why? Because the protagonist told her to watch the house.
When Train confronts Shiki near the end of Black Cat, just before his final battle with Creed, he has, depending on whether it's the manga or the anime, either the ability to fire one last nanomachine-powered railgun shot for the day or an Orichalcum bullet that can pierce any object. Just before the fight actually starts, he ends up firing it into the sky instead, just to show that he doesn't need it to beat Shiki or Creed.
In Puella Magi Madoka Magica, Sayaka refuses to replenish her strength with Grief Seeds, just because Homura uses them and Sayaka doesn't want to be anything like her. This was a very poor decision.