(Not sure if this is worth a trope on its own, or if it should be folded in to another) Most of the main cast is down. The Big Bad's powers are too strong and too confusing for anyone to defeat! All hope seems lost when the Idiot Hero arrives to challenge him. But wait! He just figured out a way to dodge an attack that was supposed to be undodgable, stunned him by reflecting his hypnotic gaze back at him with a shiny object, and bypassed his magical barrier by making his weapon wet! Wasn't this guy supposed to be an idiot? Even The Smart Guy isn't this good! May be Book Dumb or employing Obfuscating Stupidity. It's possible that activities outside combat don't interest him, in which case he is a Blood Knight, or that he merely feels he must throw everything he has into fighting, in which case he is a Determinator. It's worth noting that despite having such a knack for combat, a character of this type will rarely fight with anything resembling a formal style, instead relying on instinct and improvisation. Characters of this type are usually receptive to Training From Hell, and sometimes need a Combat Commentator to make it clear what they're doing. Common in Shonen series. See also Idiot Hero, Awesomeness By Analysis and Lets Get Dangerous.
- Goku of Dragonball Z and associated shows. He's a bit of a simpleton when he's not actively in battle mode but when fighting he's almost a different person.
- Luffy from One Piece falls under this. Practically the only time he shows more intelligence than your average five-year-old is in battle. Not only does he constantly find new interesting and creative ways to use his Rubber Man powers (he starts out just stretching his arms really far to hit harder, but later he's using himself like a slingshot and making his blood pump faster to speed up his reactions), he's even shown a mind for strategy. For example, when fighting a mind-reader who keeps predicting his attacks, Luffy just starts punching randomly so his attacks reflect off the walls, since he himself has no knowledge of trajectory and thus no idea where his punches will go.
- Naruto - outside of battle, his "intellect" ain't that impressive. In battle, he shows strategic skills that catch his enemies by completely by surprise.
- Mega Man in Bob And George. Justified via Sure Why Not in that he's programmed with the primary objective of defeating the Robot Masters and the secondary one of being an idiot, so he's smart when fighting villains and the rest of the time he's a moron. The out-of-universe explanation, however, is that this way the author can play up the Robot Master's quirks.
- Ichigo from Bleach. Started out as an Idiot Hero, but later uses Awesomeness By Analysis.
- In Ranma One Half just about every martial artist is like this. In particular Ranma, Ryouga, Genma, and Mousse are incredible at developing new techniques and countertechniques on the fly, but are otherwise... eccentric.
- In Tabletop RPGs, this is the usual result when an unintelligent character is played by a skilled or paranoid player.
- In Forrest Gump, Gump is praised for his military skills in Boot Camp.
- As is "Gomer Pyle" (after the Break The Fatty episode) of Full Metal Jacket.
- Hayana in Twinkle Saber Nova.
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