I've had moose and bison, but I'm not sure they count as non-standard.
Tuna and other fish, raw, are more of the "standard" sushi things so.... [shrugs]
I guess squid and eel is non standard?
Yeah, that's part of the difficulty answering question. What's standard vries a lot depending on where you are. I've never had deer, but I'm sure there are plenty of states where deer is totally common meat you can get anywhere. At one time, squid and octpus were "ewww, weird gross!" but in california, sushi is only slightly less common than gas stations. Duck is totally standard in chinese cuisine and has been forever. Maybe not a lot of people have had it, but probably most people have at been in restaurants where it's served, if they'd just think to order it. Snails, frog and cavier are all the same. Maybe a lot of people havent' had them, but it's not like it's difficult to find a place that serves them.
Cow and/or monkey brains I think are a bit more difficult to find, but that might just be my own local bias. I don't know of any resturants in my are that serve it and the only time I've ever even seen it on menu was on a cruise ship, but somebody else mentioned that they had it regularly as a kid.
Cat, dog, horse, whale and dolphin can be had in some places in the orient, but are somewhat rare because people like them and don't eat things they're emotionally attached to.
Only thing I've been offered but
couldn't do was fish eyeball. That was in Japan. I was the guest of honor and they brought out a 2-3 foot long fish that looked like it had been plucked out of the water and roasted on a BBQ spit. They offered me the eyes because that was supposed to be the best part. So there I was...looking at these fish eyeballs, still in their sockets, and probably a good two inches in diameter..wondering if they were serious or if it was some kind of practical joke on the idiot foreigner. Couldn't do it, apologized, and the girl on my right said no problem she'd be happy to take it...popped it right out and nommed it like candy.
How would you not think sea urchin is non-standard. I demand you tell me what it's like to eat that.
I live in southern california. There are places where you can leave one sushi bar and look across the parking lot to see another one on the same lot. Sea urchin, eel, squid, octopus...they're all standard fare. I have, however, had it fresh. As in, pull it out of the dive bag (difficult because the spines get caught in the bag) and crack it open fresh. After you crack open the shell, the meat rolled out in strips. We put it on crackers and dripped lemon juice on it. Wasn't very good though. Better than what you might get in a sushi bar because it's so fresh it's only been dead for seconds, but I wouldn't go out of my way for it.
Or, another one...I've also had ray fin. Don't remember if it was manta or bat ray. Is that non-standard? It's not a sushi thing, but pretty much any japanese restaurant that isn't a specialty place like sushi or yakitori will have it. But unlike sea urchin, it's actually very tasty. I highly recommend it. Some things are "supposed to be prestigious" or some silliness, but are awful. Like caviar, and chocolate covered ants. Caviar is like salt water with texture and chocolate covered ants taste like ammonia. Ray fin, however, is very good. If you ever have the chance, try it.