Well you're on the right track now but still I don't think you quite have what I mean.
Nice try DaS but no cigar. As there are unconfirmed sightings all over the contenant it's too much for just one Sasquatch. Sadly.
Imagine a tree that produces a unique fruit, like lets say a donut. And there is only one of these trees. No propogation at all. Just the one single unique tree, distinctly unlike other trees.
But it doesn't have to be a tree or an animal and there much be nothing at all like it anywhere. Not man made, and I think living, or living at some point.
Black hole is a good guess but they exist elsewhere most likely so not unique in the way I'm looking for.
I've been thinking on this for a couple of days now and I can't come up with a single example of something that is unique in that way yet.