Subversion: "Try Again" Bragg of Warhammer 40,000: Gaunt's Ghosts. Looks like a Class 2 at first to everyone who meets him, but actually quite intelligent. The plot point of one of the stories in the second novel revolves around Gaunt choosing him for a mission because everyone assumes that he must be dumb because he's big. Also played with in Ezrah, who is very tall but is lanky rather than brutish.
The Ogryn race (OgresIN SPACE) generally fills this role for the Imperial Guard.
Glen Cook's Garrett, P.I. novels have several of these, most notably Waldo "Saucerhead" Tharpe and female Boisterous Bruiser Winger.
Chumley from the Myth Adventures series is a class 3, with a moderate dose of class 5 also. Moreover, as Trolls like him have long found that acting like Dumb Muscle gets them more jobs, his entire race (or at least the male half of it) consists of class 3 Big Guys.
Rachel of Animorphs, despite having more feminine tastes than Cassie, is most definitely this. She has to struggle to avoid becoming a full-on Blood Knight, and still ends up one of the chief dog-shooters and a borderline Token Evil Teammate by the end of it.
It's by preference at first, and later because the team has become so settled into their respective roles that it becomes impossible for Rachel to escape hers, despite her growing discomfort with it. A fact that she blatantly points out (while simultaneously ripping all of our hearts out) in a later book:
Cassie: What are you going to do with him?
Rachel: There's only one thing I can do. I'm going to take him back to the island and abandon him there again. And this time I'm going to make sure that he never comes back.
Cassie: You can't.
Rachel: I have to. You don't have to stay.
Cassie: Rachel, I don't think you'll be able to do this a second time.
Rachel: (Snapping) You know what, Cassie? I don't think so, either. So will you do it for me?
Cassie: (Taken aback) I...
Rachel: (After a long pause) I didn't think so.
Perrin from The Wheel of Time fills this role as a type 2 with occasional 1. He is physically strong since he was a blacksmith, wields an axe and a hammer and is slow-thinking although by no means unintelligent. There's also the Ogier Loial, who fits perfectly into class 2.
Jack Reacher is class five, as he uses his brain when he uses his muscles. His brother comes across as a Class Two, but he really can't fight period.
Butler from the Artemis Fowl series. Definitely not dumb muscle, but he certainly qualifies for this trope by taking out a first class LEPrecon team on his own and bringing down a bull troll with not much more than his bare hands. He probably fall somewhere around Class 2 to 3.
French Sci Fi novel Malevil has Peyssou: big, rowdy, lewd, and uneducated.
In Death: David Baxter or Peabody could be placed in this category.
In Septimus Heap, Nicko is type 2, being rather strong from his work at a boatyard but also often carrying the Idiot Ball.
Ham in Mistborn is a Pewterarm, which means he can burn pewter to make himself stronger and increase his endurance. He also happens to enjoy debating philosophy, making him a Class Five. While Vin and Kelsier can also burn pewter, they also have access to all the other metals, while being the big guy is Ham's only power.
Tonk Fah from Warbreaker is this trope, especially in the literal sense. Returned gods also tend to have much bigger builds that also make them stronger.
The Belgariad has a Five-Man Band within the Five-Man Band made up of Big Guys. Barak, an enormous Cherek who turns into a bear and fights with an axe in one hand and a sword in the other is The Hero, Hettar, a fast moving cavalryman acts as his Lancer, archer Lelldorin is the Big Chick, religious fanatic Relg is their Smart Guy, and Knight In Shining Armour Sir Mandorallen of Vo Mandor, who kills lions with his bare hands and threatens armies by himself is Big Squared. Not much is made of this potential band within the band in The Belgariad... but in the Malloreon sequel series prophetic demands and Big Guy stubborness leads to the Big Guys of the Belgariad's hero band joining together in a band of their own (along with Unrak, Barak's son and a Big Guy-in-training) and try to catch up with the main hero band. In The Malloreon main hero band itself, Toth is probably closest, though by this point the hero has become so lethally dangerous that the Big Guy role isn't really needed like it was in the first series (Eddings knew his tropes).
Amanandrala "Grok" Grookonomonslf of the Star Risk, Ltd. series is the Genius Bruiser version. He's an alien with some resemblance to a bear and, in a team full of badasses, ranks among the deadliest. He's also extremely good with computers and cryptography.
The Crystal has Rocky, one of a trio of adventurers, and a six foot tall, six foot wide troll. A type 2. Speaks Like This, For Some Reason.
In the Wraith Squadron novels, "unit strongman" is one of the classical roles that Piggy insists keeps coming up, regardless of how the unit changes (he's right). He was one of the originals, along with Runt and Kell (Runt is the best at strongman-type displays, Piggy hits the hardest, but Kell leaves them both in the dust with his martial arts training). In Mercy Kill, Trey Courser also fills this role. Curiously, all four are variations on the rare Type 5 — Kell and Trey are both mechanics, Kell is a demolitionist, Runt was a comms tech, and Piggy is a certifiable genius in math and basically everything else.
Thomas Tanner. Which is rather ironic, considering he was a shrimp when he was younger.
Journey to Chaos: Tiza is this for Dragon's Lair mercenary team four. As the team's fighter, her role is to tank the enemies. She wears the heaviest armor to absorb damage in place of the mages and fights up front with sword and shield. Her teammates support her with healing, buffs, and coverfire.
In the Dred Chronicles, prison gang leader Dred has Einar, one of her lieutenants and bodyguards. He can act the Gentle Giant when he wants, but as Dred notes, people like that don't end up where they are and survive.