@tardis well, Hungarian [Finnugric], Basque, Navajo [Athabaskan] are good examples.
In fact Basque is probably the language isolate with the largest speaker base.
https://en.wikipedia.org/wiki/Language_isolate
But... unique may mean something else. Chinese is unique for its tonal system, or any in the https://blog.pimsleur.com/2020/09/29/worlds-most-unusual-languages/ list. I doubt you'll find many material to study of those, though.
@tardis Funny, but Hungarian is said to be somewhat similar to Bulgarian (as for agglutination):
https://www.youtube.com/watch?v=Wh8PUImUMYo