If we're including captive animals, the one that stands out the most to me is a Chaco Owl. It's not considered endangered yet, but it's only found in one particular area of the world, at the borders of Bolivia, Paraguay, and Argentina.

In the wild, I've come across porcupines on a few occasions, and I almost had a fisher cat run up my leg. I didn't know we even had them in my state, so I was very freaked out as to what this long, furry thing coming at me was. I wish I had maintained my composure so I could have gotten a better look at it, but it's also the kind of thing in glad we figured out what each other was before I was in biting range!