“Uncommon” is a relative term. Things that are unusual in one place or time might by common in another. That being said, the uncommon foods I’ve eaten include:
I often eat other things that some might consider uncommon, like nopales (cactus leaves) and bitter melon. These aren’t so unusual where I live, though.
I once made a list of mammals I’ve eaten. It included whale, seal, moose, caribou, camel, guinea pig, squirrel, bear, bison. Animal parts including cow brains and placenta, sheep eyes, hog penis. Cod tongues and cheeks, and many kinds of vaguely- or unidentified raw seafoods, like barnacles and sea urchins. Cooked potato leaves, green wheat bulgur, raw green almonds. Unknown insects and larva. I eat banana peels at home all the time, and apple cores.
Chocolate covered ants in 6th grade. Rattlesnake and alligator at a party. Emu and ostrich at restaurants (not sure if they qualify as uncommon or not - both are really good.)
And yummy pig’s stomach which is part of my wife’s tradition. Can’t make it here since no one sells the stomach intact.
I’d think that potato leaves are poisonous. It’s common knowledge that potatoes that have turned green can be toxic, and I would think the leaves would be even worse. What makes them edible? Does something in the preparation destroy solanine (the alkaloid common to members of the nightshade family)?
I’ve eaten squirrel, chocolate covered bumblebees, geoduck clams, and fish head stew (although to be fair, I ate the stuff around the fish heads, not the heads themselves)
It’s not super uncommon now, but it was new/rare when I had bison steak. Twice. At Top of the World. After its ahem ratings fell, I was unable to order it for years.
Cozido: it’s a traditional Portuguese peasant dish, made mostly with parts of the pig that you wouldn’t normally eat. I nibbled at it a bit, but it was making me queasy.
A mixed seafood plate in Greece that had octopus the consistency of rubber and fish that was bony to the point of being inedible.
Bacalhau con natas (salted cod with cream). Another Portuguese dish that, to me, is inedible.
I was told (in French) they were potato leaves, but since it was in Benin, I strongly suspect they were sweet potato leaves, which are in a whole different family. Sorry to have misled you, my bad.
My father was a hunter, so we ate a lot of wild game. Elk heart was probably the most uncommon item; it was actually quite good. He bagged a mountain goat once, which wasn’t so great.
Where I grew up, that wasn’t uncommon. Nor was caribou. It’s funny that those didn’t occur to me as being uncommon, but I guess they are to most people.