The Eyrie's jailer Mord may even be mentally retarded, but is big and strong enough to be competent at his job. He's also nearly too dumb to bribe.
Hodor isn't very intelligent, but he can rip chains off the wall and pulverize the throat of a strong and skilled man. He also stopped a wave of wights pushing down a door to the point the wights had to break the sides of the door and slice him up to advance since they couldn't simply push him down.
Lorch is a competent warrior and certainly has his uses...relying on his brain is not one of those uses.
Gregor is a killing machine with little to no sense of tactics or restraint, as he's too Ax-Crazy to consider whether his acts of brutality are actually detrimental in the long run. Nor does it seem likely that he cares, it's not like the Lannisters pay him for being smart, his job is to apply Disproportionate Retribution to those who cross the family. After his transformation, Qyburn implies he's even dumber than before as the "experiments" he did to save him affected his mind, and most of his free will appears to be gone, becoming instead an obedient drone.
Babylon 5: The Legend of the Rangers. "My name is Tirk. I carry heavy things."
Buffy the Vampire Slayer: Glory constantly underestimates her opponents and acts without thinking. The only thing that makes her a threat is that she has a lot of muscle.
You can also see the half-demon Groosalugg in Angel. As a half-demon, he is really strong, and in his homeland he was even known for being a legendary warrior who has destroyed every monster he has ever fought. He is not necessarily stupid, he just does not like to use his mind when he fights against demons.
Ronon from Stargate Atlantis. Played for Laughs at times and sort of justified because of his past. His "plans" often contain simply Stuff Blowing Up or killing the enemy instead of (necessarily) working together and he's very unwilling to try a more intelligent method. However, he seems to work great with McKay.
"Mission Report: Michael invaded Atlantis. Tried to blow it up. We stopped him. End of report."
Firefly: Jayne appears to be this at first; a moron whose skills are limited to hitting and shooting stuff. But don't be fooled. Over the course of the show, he's demonstrated that he's a reasonably-cunning planner, a skilled tracker, and a capable pilot. Admittedly, he's not academically bright, but he's very knowledgeable about a lot of practical skills. He's also shown to be an impressive judge of character—seeing through Dobson's lies instantly, for example.
Finn from Glee is a six-foot-three athlete who isn't exactly the brightest bulb in the bunch.
Ogrons, a species of gigantic caveman types used as muscle by the Daleks in the original Doctor Who.
Incidentally, in a metafictional in-joke, "OGRON" is the name of the Soviet equivalent of UNIT (Operativnaya Grupo Razvedkoy Obyeddinyonnich Natsii: United Nations Surveillance Operations Group).
Troy on Community is a classic example. God bless him, he is not the brightest bulb in the box.
Brazilian group Casseta & Planeta had Carlos Maçaranduba, a stupid muscle-head with a penchant for violence (parodying the local subculture of the "pitboys")—and anything he deems doubtful of his masculinity leads to a beating. His friend Ulson Montanha is only slightly smarter.
Angel: The Beast in Season 4. Just the fact that he has a long-term plan other than mindless slaughter and wanton mass destruction is a sign that he's working for someone else.
This is zigzagged with Gunn, who seemed typecast as the dumb muscle (and he is Genre Savvy enough to be aware of this). That is, through the end of Season 4. The upgrade that Wolfram and Hart gives him is to make him into the brains of the outfit, the Ace Attorney.
The final season introduces Choo-Choo, so named because when he hits you, it's like you've been hit by a train.
Ryuga Banjo, the Second Rider of Kamen Rider Build, is as dumb as a sack of obsolete encyclopedias and has a mean temper; the title character even explicitly calls him thisnote Kinniku baka, literally "muscle idiot". On the other hand, he also has suprising amount of insight and intuition, provided his temper doesn't get in the way.
In Supernatural, the Men of Letters saw hunters as brutish but necessary.
Played with on Chuck with John Casey (another Adam Baldwin character). As he's played by all 6'4", 230 lbs of Adam Baldwin, Casey is without question the biggest and strongest member of the team (Zachary Levi is quite tall as well, but not nearly as powerfully built), shown to be able to resist multiple tranq darts, and many bad guys just injure themselveswhen they try to punch him in the face. He also once ripped an old-style radiator out of a hotel wall after he was cuffed to it and used it as a weapon while still cuffed to it in the subsequent fight. However many laughs are also had at his expense over not being as bright as Chuck and Sarah, even failing an aptitude test miserably with the lowest score ever recorded when he and Chuck are trying to infiltrate a Fulcrum recruiting center. The played with comes in that Casey's is actually closer to average in intelligence, well-trained, and capable of thinking quickly on missions. It's just that many of his associates on the show are unusually intelligent and highly-technical people due to the nature of the assignment, so his main role on the team is acting as the muscle while Chuck and Sarah usually handle the finesse.