Wheel of Pain

Mandatory torment of ancient and fantasy slaves. It's a giant capstan to which slaves are chained and made to drive in order to power some unseen machinery. In Fictionland, it seems, every slave-holding culture has this device. The most notable exception are the slaves held on plantations in the antebellum South of the United States.

Can occasionally happen in a futuristic setting. These wheels often don't even do anything; presumably they're only used because the bad guys are just dicks.

Has nothing to do with Painwheel.

Examples of Wheel of Pain include:

Anime and Manga

Dai Mahou Touge Omake had this in the Fantasy Kingdom.
In Bizenghast volume 3, the characters are forcibly chained to one of these.
Electricity in Tentei's Capital in Fist of the North Star comes from such contraption.

Film

Named for the device from Conan the Barbarian, which turned the titular character from a scrawny kid into the musclebound Badass that rampaged across two films. (Indeed, Arnold Schwarzenegger buffed up so much for the movie, when he was being filmed pushing it along, the director had to have half the crew on the other side of the wheel pushing the opposite direction so it'd look like Arnie was actually exerting himself.) According to Word of God, it's a grain wheel.
Used on the sugar plantation the eponymous protagonist is chained to in Captain Blood.
Zombie slaves provide the motive power for a similar sugar-mill capstan in White Zombie (1932, and not connected with Rob Zombie beyond a A Good Name for a Rock Band).
- There's a surprisingly grisly moment for the era the movie's in when one of the zombies falls into the mill and is mindlessly ground up by the rest.
Pirates of the Caribbean: Dead Man's Chest had the Kraken-summoning machine powered by the ship's crew.
The Lord of the Rings: Return of the King had trolls turning huge wheels to open the gates of Mordor.
The film adaptation of the musical Oliver Twist briefly shows a variation on the theme, as detailed in Real Life below, during the opening scene.

Literature

The Great Wheel of Kharnabhar, in Brian W. Aldiss' Helliconia trilogy, is built inside a mountain, has only one door, and takes several years to make a turn. The locals believe the Wheel drives Helliconia's great year, so in the centuries-long winter when things are bad for humans, the Wheel is basically a monastery staffed by volunteers; in summer, it's a prison.
- Which opens another question: How the hell was this thing built? And after it was finished, how was it put into move, since it's harder to make something move than keeping it moving?
Shows up a couple of times on Gor: the gate that one enters the Sardar Mountains at is powered by slaves, and in Guardsman of Gor the hero is captured and set to work one which opens & closes a water gate. Don't worry, he planned for that to happen in a Xanatos Gambit.

Live Action TV

Doctor Who has the Christmas special "The Next Doctor", with orphans turning this this type of device to turn the machinery to start the Cyber King.
True Blood, but not before the second season. Actually, Godric have one in the basement of his bar.

Religion

Samson, after being captured by the Philistines and blinded, is set to work on one of these.

Video Games

In The Curse of Monkey Island, the player sees a horde of monkeys being enslaved this way.
One of the first missions in Brutal Legend involves freeing a bunch of Headbangers from a mine that features one of these.
In Dominions 3, Early Ulm has it as one of their national sites. Orphans are sent there, and those who survive are made into Steel Warriors, often called "Conans" by the fans.
A non-slavery example can be found in The Legend Of Zelda: Wind Waker. Tingle's brothers are responsible for keeping his lighthouse spinning. They aren't all that happy about it though.

Western Animation

King Bumi's pet, Flopsy, was chained to one of these in Avatar: The Last Airbender.
Samurai Jack found his father chained to this device by Aku.
Spoofed on The Simpsons, where Homer is forced to work one, which turns a display wheel at the canteen.

Lenny: Hmm, I wonder what makes the cupcakes turn.
Carl: Who cares?

One of these showed up in a recent episode of Futurama.
Cobra from G.I. Joe in many of its earlier episodes inexplicably kept haggard looking slaves wearing rags, turning wheels and pushing mining carts, despite that fact that Cobra prided itself on using the sorts of advanced technology that would have made it easier to mine via automation.
One episode of The Fairly OddParents (the beauty pageant episode) had one of these in every character's fantasy of them becoming mayor for a day. In Vicky's fantasy, Timmy is the one turning the wheel. In Timmy's Mom's fantasy, it's Timmy's Dad and Timmy turning the wheel. When Timmy's Dad actually wins the contest and becomes mayor for a day, he basically makes the fantasy come to life... only it's his hated neighbor, Mr. Dinkleberg turning the wheel.
- At one point in Wishology, the fairies are forced to do this by the Eliminators. Cupid asks "What happens if we stop pushing this thing?" They decide to find out...and discover that it plays the melancholy background music.
In My Life as a Teenage Robot, when first informed about the Cluster, we see humans chained to this, apparently to power some kind of Ice Cream Parlor for robots.

Real Life

Something similar in principle was actually seriously proposed for use in workhouses in Victorian Britain, not for slaves, but for petty criminals and/or the long-term unemployed. (The two groups were treated pretty much the same back then.) It used a treadmill arrangement that resembled nothing so much as a very large hamster-wheel rather than the traditional capstan, which really isn't very much better, and rarely if ever served any practical purpose because steam power did the same job more effectively.