Curse Quest: Considering Captain Walrus acts as the leader of the team, he definitely fits the bill. He can't tell apart a witch from a sorceress, was tricked into eating slugs and doesn't realize the obvious red flag of Avalon wanting to return to the Land of Avalon to kill the evil ruler of the Land of Avalon. The Owl Hunter is no better a hero than he is. Also during Quest-Con, all the heroes that are at the tavern don't realize that they are being attacked by actual owl-bears, which is partially affected by their drunkenness, but Avalon is quick to point out that alcohol is not the only culprit.
Requiem: They don't realize those ulvorn are real? Are they just too drunk? Or stupid? Avalon: Some are both. (Glaring judgingly at Walrus.) — Requiem and Avalon after the owl-bears break into the tavern.
Jim's characters in Darths & Droids, since he likes to turn his brain off whenever he's in RPG mode. It goes double for Han Solo, since Jim is actually trying to play him as an Idiot Hero thanks to his low Wisdom and Intelligence scores — though it should be said the other players don't immediately notice the difference. Subverted when it's revealed Han has been making stupid choices that lead to trouble because he's a traitor. This revelation doesn't make him stop being stupid afterwards.
In Exterminatus Now Rogue's temporary Replacement Scrappy Yuri "Wildfire" Keila. She was so stupid, The team had her chloroformed, passed of as injured (complete with full body cast), and sent back to Taika in exchange for Rogue, who they, after what Wildfire's done, are delighted to see.
Lothar:(after Wildfire's stupidity has ruined their mission) New rule: No member of the team is allowed more beam swords than brain cells.
Girl Genius has Othar Tryggvassen, Gentleman Adventurer! He has some tendencies towards this trope at times, especially in his own adventures. At one point, he's trying to find and stop the Weasel Queen. He finds a woman with weasel ears and a throne. Conclusion? She must be a Damsel in Distress! Othar is Too Dumb to Live in the Girl Genius world. It's a good thing he's also the Determinator. In the GG comics, Othar isn't The Hero. He's barely A Hero. He's comic relief, and he's dumb to serve the Rule of Funny. In the twitter adventures, Othar is the hero, and he's written as fairly confident and clever, only getting into scrapes because he's a sparky Gentleman Adventurer. (though the twitter is also written byOthar, so take it with a grain of salt). Finally, he's absurdly competent at few things, though. Such as surviving being thrown out of an airship (this happens to him with Running Gag frequency).
In Greg, Gregorious maintains his idiocy throughout the Medusa story arc by repeatedly falling victim to Medusa's nude charms.
In the very first chapter of I Love Yoo as the main character gets introduced, this trope gets Zigzagged so quickly the reader gets whiplash. It goes something like this: First Shin-Ae gets a test back while the teacher says "50%". Next panel, it turns out that was the class average, and Shin-Ae confidently thinks she must have gotten at least 85%, because she spent so long reading for it. Turns out she got 68%. In the end, it's left unclear whether she's an idiot or not, and it's not until several chapters later that it's definitely established. She's not.
Kubera: Leez is more ignorant than idiotic, having flashes of brilliance when she's allowed enough information to work with and time to think. It's all but stated that she plays this up because she's a Stepford Smiler.
Dhur of Meat Shield is fairly dim, being a half orc barbarian and all.
Elan: Nale! You're alive! Nale: Of course I'm alive, you moron. What I can't figure out is how you didn't know I was alive the whole time. You're the bard, surely you should have known that when a bad guy dies off-screen, he's not really dead unless you see the body. And half the time, not even then. Elan: Yeah, but the hero always THINKS the bad guy is dead until he shows up again. Nale: But... If you know that, how can you be surprised... Why didn't you realize that you thinking I was dead was... I mean... Gah! I'm giving myself a migraine just trying to understand the level of willful ignorance that requires! Elan: First blood: Elan!
Kedamono from The Pride of Life; his heart's in the right place, but his first attempt at heroism ends with him mortally wounded, and he only survives because the person he was trying to save was able to staunch the bleeding long enough for the World Tree's fruit to kick in.
Both of the protagonists in Skullkickers, although Shorty more so than Baldy. They're actually extremely competent, they just aren't very bright.
Readers: Why does the human [fill in the blank]? Writers: Because he's not very smart. Readers: Why does the dwarf [fill in the blank]? Writers: Because he's stupid.
Torg from Sluggy Freelance. He Took a Level in Badass as well, and does smart stuff sometimes... but reverts right back. Bun-bun can't decide whether it's an act. The real answer is probably one he has practically given himself: he doesn't like to think and prefers to avoid it. When he actually makes the effort, though, the results are either as good as for anyone else or downright brilliant in a weird kind of way.
Supporting Leader Ben from Weak Hero isn't the smartest cookie in the jar, but he makes up for it with his stupendous strength and upbeat personality that garners people's respect and keeps him strong even when the going gets tough.