What An Idiot / Rurouni Kenshin

• Kenshin and Shishio are on their last legs. Shishio's 15-minute limit has already elapsed. His right-hand man, Houji, has a rifle.
  You'd Expect: Yumi: "Just Shoot Him!"
  Instead: Houji: "I believe in Lord Shishio!" [throws his gun away]
  The Result: Shishio: Man on Fire
  To Make Matters Worse: Previously on the Great Kyoto Fire chapters, Houji modified Shishio's original plan by arranging that 7 members of the Juppon Gatana took part of the Great Kyoto Fire by killing the police officers and VIPs as a distraction while the rest sail towards Tokyo to bombard it and thus destroy it while the capital was undermanned. He did this because he wanted to bring total victory to Shishio regardless of costs and perhaps even risking gaining his ire modifying his plan in such a manner. Before the final fight with Kenshin, Houji swore that he would risk being hated like snakes and scorpions as he put it and had his rifle in hand in case the worst would come to worst! By pulling his Honor Before Reason moment, Houji completely contradicted himself in this double whammy of the most illogical, thus bringing us this moment. Holy crap.
• Similarly: Saito has just gained the advantage of surprise by suddenly appearing on the battlefield.
  You'd Expect: He'd go for Shishio's heart. Or pretty much anything vital in that area.
  Instead: Tries to stab him in the forehead for some reason. So he hits the only armored part of Shishio's body. And due to Shishio's ability to beat any attack he's seen once, even his Zero Gatotsu fails (an Ass Pull in itself) and that's pretty much it for him in the fight.
• Said above battle: Shishio has managed to KO Kenshin, Saito and Sanosuke in rapid succession, and he himself is barely winded after all that. Yumi then urges Shishio to just hurry up and kill them.
  You'd expect: For Shishio to, y'know, do exactly that.
  Instead: Shishio declares that he's having too much fun and wants to savor the victory. This attitude allows Aoshi (who'd earlier undergone a full Heel–Face Turn) to come to the arena and fight Shishio in order to buy time for the others' Heroic Second Wind to kick in.
• Way back in the first major arc, with Jinei Udo, a Revolution-era hitoriki like Kenshin, whose only real edge against Kenshin is that he hasn't lost his knack for killing. Jinei has managed to establish himself as a serious threat by slitting both of Sanosuke's wrists at lightning speed (in the manga, he stabs Sano straight through one wrist in graphic detail). Kenshin decides to take the one-day time period Jinei's given him to prepare, to go psych himself mentally to face the villain, but before doing so, he tasks Sano with letting Kaoru know the situation, which Sano does.
  You'd expect: That once Kaoru's told what sort of enemy Jinei is, she'd heed Sano's warning and stay put so as not to get Kenshin distracted and in trouble.
  Instead: Kaoru decides to go to where Kenshin is on the off-chance that he might leave and never return after confronting Jinei, even after Sano shows her his own injuries to emphasize that Jinei's not a nice guy.
  Result: Kaoru gets kidnapped and held as bait by Jinei, triggering Kenshin's Battousai personality when he sees it happen.
• Same scenario: In the manga, right after Sanosuke explains to Kaoru what Jinei's all about, she chases after Kenshin with the justification that she'd rather risk her life than risk being left all alone should Kenshin decide not to come back if he survives the fight.
  You'd expect: Sano and Yahiko to chase after Kaoru, force her back to the dojo, and remind her that (A) Kenshin hasn't given any indication that he won't come back, and (B) she still has the two of them, at least, to keep her company.
  Instead: They let her go, with Sano reasoning that since it's love motivating Kaoru, they wouldn't be able to change her mind. (In the anime, they at least bother to go searching for Kaoru once Kenshin sends word of her being kidnapped, though in the end they don't impact the main plot anyway.) Although the manga's version of that scenario might be mollified somewhat because Jinei was spying on them at the dojo anyway; one panel in that scene reveals he's hiding in the trees nearby and eavesdropping on the conversation.
• During the Kyoto arc, Sanosuke meets Anji, a fallen monk and (unknown to Sano at the time) the third-strongest member of the Jupon Gatana, while Anji is training his Futae no Kiwami technique. Sano asks to be taught the technique, which Anji relents to after some persuasion. After grasping the basic idea behind the Futae no Kiwami, Sano trains relentlessly with his right hand until he's mastered it within a week.
  You'd expect: For Sano to at least train the Futae no Kiwami with his left hand, as well, so that by the time the final confrontation comes about he'd be able to use it with both fists. It's not like he can't effectively give a left-handed punch, after all.
  Instead: He only focuses on his right hand and none of his other limbs.
  Result: He overuses the Futae no Kiwami with his right hand during his fight with Anji, eventually breaking it when he tries to challenge Shishio. The damage ends up becoming liability in the Jinchuu arc as his hand now explodes every time he uses the technique until he devises an alternative to lessen the damage.
• During the Jinchuu arc, Saitou determines that Enishi is going to try to kill Kaoru to get to Kenshin, and suggests to her that she should flee.
  You'd expect: For Kaoru to take Saitou's advice and run. She's not a very powerful fighter, in contrast to Enishi and his allies, and if she were to flee from there Kenshin would have one less distraction to worry about while fighting Enishi.
  Instead: She stubbornly refuses to leave.
  You'd then expect: For Saitou, who's not quite as badly injured as the other fighters up to that point, to do his job as a cop and forcibly take Kaoru away from the scene, or, failing that, to play bodyguard for her so Enishi can't get to her.
  Instead: Saitou coolly tells Kaoru that since she won't leave of her own volition, she shouldn't expect him to move a finger to save her.
  Result: Enishi kidnaps Kaoru and leaves a lifelike doll of her with his sword through its chest to plunge Kenshin into a Heroic BSoD. It might have easily been Kaoru getting killed for real, but luckily for her Enishi couldn't bring himself to do it since she reminded him of his own dead older sister. Saitou never gets called out for his callous indifference, which as a cop should have at least gotten him into trouble for negligent homicide—not being more proactive to stop a murder he knew was intended to take place.
• During the Saitou vs. Usui fight, Usui manages to wound Saitou in both legs and deflect Saitou's signature Gatotsu thrust twice with his tortoise-shell shield, then shoves the shield right up in Saitou's face so his field of vision is completely blocked.
  You'd expect: That Usui, who Saitou can't see behind the shield at this point, would just kill him right there and then.
  Instead: Usui takes a moment to brag that he can attack from any angle behind the shield, and that Saitou's Gatotsu is now nullified since he can't use it at such close range.
  Result: Saitou shows him that he does in fact have a close-range version of the Gatotsu that doesn't require a running-start, pinning Usui to the wall (and ripping him totally in half in the manga).