It could be claimed that liver barely qualifies as an exotic food, as it has to be the most common (or at least among the most common) consumed organ. But, on the other hand, many folks do consider it distasteful, if not revolting. Additionally, I'm running out of organs to write about, so here we go.
This immense organ (largest of the internal organs, and second in size overall to the skin), has several functions, including detoxification, production of bile, and protein synthesis. It also has several traditional, cultural interpretative functions. People in Iran, Pakistan, and India have considered it to be the source of courage. The Jewish Talmud lists it as being the source of anger, in direct contrast to the gall bladder. The Persian word for it, "jigar" is used as an adjective for things considered attractive and desirable, including women. The Greek God Prometheus, credited with providing fire to humanity, was of course punished by being chained to a rock, where every day his (constantly regenerating) liver is savagely eaten by a giant eagle. (I always wondered--wouldn't the eagle get bored by this same meal every day? If it was me I think I'd occasionally eat Prometheus's heart, or tenderloin, or something else just for variety's sake.)
Moving to historical figures, American Western mountain man/hunter/trapper John Johnson (almost certainly an alias), said to have lived from 1824-1900, acquired the nickname "Liver-Eating Johnson." After his Flathead Indian wife was allegedly killed by some Crow Indians, he's said to have embarked on a twenty-five year period of revenge against them. After killing the Crows, he supposedly cannibalized their livers, since in their belief system a person needed that organ to continue into the after life. Another account has him kidnapped by some Blackfoot Indians, who planned to get a reward for delivering him back to the Crows. Johnson purportedly managed to escape, and ate the leg of one of the Blackfoots, this time more for survival than for insult and spiritual punishment. The successful 1972 Robert Redford movie "Jeremiah Johnson" is based largely on Liver-Eating Johnson, but for obvious reasons they didn't include his cannibalistic exploits. (Although I think it would have been awesome if they had.) Also, Johnson is thought to have been born in my home state of New Jersey, so represent and all of that.
But back to the actual food. The livers of many animals (cows, pigs, sheep, various poultry and fish, etc.) are commonly consumed. I've had them from cows, turkeys, chickens, and geese. There's no denying that it has a distinctive, "organ-y" texture and flavor, which obviously many people find off-putting. I enjoy it, but it's not something I could eat often--generally once a month at most. Liver and onions is a traditional meal, and a nice, effective flavor pairing. I've had the chicken and turkey livers as part of giblet gravy, which is one of the better gravies. I also like liverwurst, usually as a sandwich, with mustard and sometimes onion again. Liverwurst is a more milder form of liver--I ate it for lunch lots of times as a kid without realizing it was actually made from liver (I know, I know, it's right there in the name--I was young and naïve). Goose liver, in the form of pate, is another way I've had it, and is also tasty. It's almost earthy and rich, and is a nice appetizer spread on a cracker. I've never had the opportunity to try foie gras (due to various animal cruelty laws, rarity, and cost), and probably wouldn't even if I could. Clearly I don't have an issue with eating animal flesh/products, but I would probably draw the line here. Force feeding using essentially a funnel (the gavage) stuck down a goose or ducks' throat does sound cruel, and perhaps unnecessary, as apparently you can get a similar effect just by letting the animals gorge of their own accord. And of course, no mentioning of eating this organ could fail to cite fictional character Dr. Hannibal Lecter, he who loved his census taker's liver, "with fava beans and a nice chianti." I'm not writing this blog post from a prison cell, so I haven't tried human liver myself. And like the foie gras all over again, there'd be severe moral implications with cannibalism, so it's safe to say this won't ever change, barring a gun to my head, or being in a plane crash in the Andes, or something.
Healthwise, liver has several nutrients, such as Vitamin A and iron. And obviously cod liver oil is a common vitamin supplement. One warning though--getting too much Vitamin A can be toxic, or even fatal. Certain animals' livers, including polar bears, seals, moose, and huskies (yes, the dog) have unusually high Vitamin A concentrations, so these should be strictly avoided. I realize that probably very few of the readers of this blog live in areas where these species live, or are part of cultures that would conceivably eat these animals, but still, a warning's a warning.