In One Piece, Eiichiro Oda takes a fairly standard shonen manga trope, that of the dim-witted but strong hero, and makes it sing with Monkey D. Luffy, a boy who has the ability to stretch his body in all manner of crazy ways, and uses that power in his quest to become "King of the Pirates". It's tough to sell the effectiveness of a dumb character like this, but Oda manages by giving Luffy a ridiculous amount of determination, and also managing to surprise with what he's capable of.
Take this sequence, in which Luffy and his compatriots are facing off against a band of pirates led by a master hypnotist, who puts his minions into a trance to give them super-strength, but also causes some unexpected results:
I love the way Oda sets up expectations that the heroes are going to have to face a big threat, then immediately upends it by having Luffy save the day through his dumbness. And the payoff for that is hilariously nuts, with Luffy attacking the pirates with a flurry of punches that send everybody flying; it's enough to evoke astonished laughter from the reader. How Oda manages to do this sort of thing constantly throughout the series is pretty impressive; in only a few short volumes, he establishes himself as a master of comic timing. No wonder people like this comic so much.