Not unknown, but three vegetables I like that seem to be not as widespread outside Germany (though at least in the USA, all seem to be available):
Kohlrabi (seems to have no English name), texture like a very solid apple, but tastes more cabbage-y (German Kohl means cabbage). Great raw and cooked.
Pointy cabbage. Like normal cabbage, but more delicate, including in taste. Requires far less cooking (steaming is best).
Savoy cabbage: looser than normal, and very crinkly leaves. Works better than other cabbages in creamy sauce.
So, uh, I like cabbages and we have a lot of them here ;)