Captured by Cannibals

"De cannibals is hungry and de whites am in a stew."

—Little Nemo (1908 musical version), "Cannibal Barbecue"

One specific, discredited version of I'm a Humanitarian is the idea that when missionaries or other people from the "civilized world" encounter "natives" in a locality, they are in danger of being eaten by them. They may initially think they are being treated as a respected guest or even a god, but then, without fail, out come the pots and the chanting.

Sometimes, the eating aspect isn't as stressed, but the idea remains that the outsider will be attacked and sacrificed instantly upon entering foreign territory.

Film

Pirates of the Caribbean had this with a tribe that captured Jack and several of his crew. This example is a good illustration of this trope being discredited. At first, the natives doing this were identified as Caribs, and the few surviving Caribs complained that they were cannibals is a false accusation against them.
Muppet Treasure Island has an isle of wild boars who worship Benjamina Gunn (Miss Piggy) as a god, and attempt to cook the heroes. Naturally, the Swedish Chef is on the island as their chef. Definitely played for laughs.
Bob Hope and Bing Crosby are captured by cannibals in Road to Zanzibar. The cannibals think Hope and Crosby are white gods... until, that is, the cannibals decide to test their divinity by having Hope get into a sidesplittingly hilarious wrestling match with a gorilla.
Cannibal Ferox
The entire second half of Cannibal Holocaust.
Prisoner of the Cannibal God
Sin City has a variation of this. One of the protagonists and his parole officer are trapped by a cannibal Serial Killer and the occaisional cannibal cardinal. Unlike most of the examples here, they weren't a part of a native tribe. They were just crazy.
Spoofed in Surf's Up. Chicken Joe is captured by native penguins who put him in a pot, which the oblivious Joe mistakes for a hot tub. He eventually befriends them with roast squid on a stick, which the natives find it Tastes Like Chicken.
Played with in the second Crocodile Dundee movie during a scene where Mick's Aborigine friends (one of which is called Charlie by Mick) are holding some of the drug lord villain's men prisoner.

[first Aborigine speaks in Aborigine language]
Charlie: No mate we just hold them.
Sue: What did he say?
Charlie: [winks] He wants to know if we're allowed to eat these men.

Literature

Actually used fairly straight in two novels of The Culture. In Consider Phlebas, the protagonist encounters a group of natives who are at first welcoming, but then try to eat him. He literally pulls Regret Eating Me on them, as his Bloody Murder powers ensure death to anyone taking a bite of him. Also, in Use of Weapons, the protagonist is tortured and sacrificed by natives on a planet he lands on, and is down to Losing Your Head by the time he is rescued, and needs a new body as a result.
In Evelyn Waugh's novel Black Mischief, the black tribesman are cannibals in the fictional East African country in which the novel is set. Ultimately, one group of characters has a plane crash/is slaughtered by them, and one of the protagonists ends up eating them, not realizing what or who he is eating until the natives tell him.
In a way, this trope figures in Heart of Darkness. One of the only African characters Marlow describes as an individual is among a group of rowers for the European explorers (for lack of a better term), and they are described as being cannibals, but considerate enough not to practice that while Europeans are watching.
A non-culinary example: In Larry Niven and Jerry Pournelle's Burning Tower, Arshur the Wanderer enters Aztlan with the other heroes and is immediately crowned king. He's given four virgins as body servants, a palace to live in, everyone in the city follows his every order... and a week later he's drugged, dragged to the top of a pyramid, and is "sent to the gods" by having his heart cut out and sealed in a stucco wall.

Live Action TV

An episode of The Goodies had the lads placed in a native cooking-pot. They got out of it by encouraging the natives to cook "human clear soup" - the point being that when cooking clear soup you remove the meat before serving.
In one of the more recent Jonathan Creek episodes, the titular character's boss had got in trouble with the media for saying words to the effect of "We'll be eaten alive" while visiting an African nation (He was, apparently, talking about locusts).
The Torchwood episode "Countrycide" had the team investigating missing persons. They ended up finding out what happened to the people who went missing when they got captured themselves.

Tosh: We're food.

Captain Redbeard Rum's (offscreen) fate in Blackadder II.

Blackadder: He was a third-rate captain, but a first-rate second course.

Music

Voltaire's "Cannibal Buffet" is all about this.

Newspaper Comics

Happened a number of times to Little Nemo and his friends. One time a missionary showed up, trying convert the natives to vegetarianism.
Several stories in the early years of The Phantom featured cannibal tribes, including a few tribes in the Phantom's own neighborhood who were officially reformed but prone to backsliding when they thought he wasn't looking. (One much later story ends with the Phantom placing the villain of the piece in the custody of one of these tribes, encouraging good behaviour by warning him of their history and carefully neglecting to mention that since then not only have they kicked the cannibalism but have all become vegetarians.)
Disney does not like talking about the way Africans were portrayed in their 1930's Mickey Mouse comics. This trope has a lot to do with that.

Western Animation

Happened to Rocky and Bullwinkle. Lampshaded and Subverted when they pointed out that since they're not human it's technically not cannibalism.

Video Games

Subverted with the vegetarian "cannibals" in the the Monkey Island series. They still capture Guybrush, but afterwards they stand around and debate whether or not it would be healthy to eat him.
Your explorer can be captured by a cannibal tribe in a certain Random Event in The Wager. They won't eat you, but if you don't have the proper items or pick the right choices in the event, some of your crew may suffer horrible fates.