Probably a mole. Not rare in itself, but as they mainly chill in their caves, seeing one by just walking on an official track in a forest is probably relatively rare. The cute fella just stuck his head out, and before I couldn't really react, he apparently already heard me and vanished again.

When entering the Everglades NP my girlfriend and I were handed one of those folded maps with info on the park. Early 90's BTW. We went to a campground and set up our tent then soon decided to drive out of the park to buy groceries. On the drive out we saw a convertible pulled over to the side of the road, it's occupants looking at something. We looked and I saw the back end of a large cat walking away. My first impression was who could abandon a cat here? It will get eaten by alligators. Soon I realized it was no ordinary house cat. The brochure we were given stated there were nine known Florida panthers left in the million acre park.

I got to see one of the last few white rhinos.

Probably a sea turtle. Was snorkelling in Malaysia, completely obsessed with the coral and all of the fishes, when this massive turtle just cruises by. Held my breath for as long as I could to swim next to it, not too close but just wanting to be in its presence, it was so calm and majestic as it headed out into the deeper ocean

Not sure how rare they are, but it was rare for me

https://wildsafebc.com/species/rattlesnake/

Giant hornet. Easily 4 inches long. I have no idea what it was doing in California.

Hmm, I am not sure I've seen anything rare, though we do have some animals in Florida that I don't think are everywhere, have seen wild manatees and alligators, those enormous Sandhill Cranes and pink spoonbills, lots of lizards and snakes.

The animal I have personally seen, but most rarely though, is a fox. Have only seen one wild fox in my over 50 years.

Giant Millipede and Armoured Millipede. Not the rarest but you will never seen one without going into the forest.

African penguins maybe? They're endangered. I took my partner to feed them at an aviary.

I feel like I've seen a black rhino before, maybe at the San Diego zoo as a kid or something. Those are critically endangered, all but one subspecies extinct.

Probably wild camels in central Australia or a platypus when I was young.

Desert tortoise, and an old one at that. Was bigger than a basketball.

Saw a lynx cross the road ahead of us in the Yukon.

Probably a California Condor at the San Diego Zoo.

Wild turkey.

I saw a melanistic eastern grey squirrel this summer, which Wikipedia tells me has a prevalence of about 1 in 10,000. It was just pokin' around my campsite when I woke up one morning. Oh! And I just remembered seeing eyeless fish and salamanders in caves.

A wolverine. A kamoshika.

Used to have a bush about 5 feet from my bedroom window that Cardinals would nest in.

In my area,

Pheasants and peacocks

The Chirping Dog

Probably a gila monster

On a Boy Scout camping trip someone brought in a wolf in a cage, so maybe that. Otherwise it'd have to be the day last spring that a few turkeys decided to show up at the college I go to and peck at one of the doors in the building I was in.

Might not fit in this thread but here goes.

My family used to have a cabin that was at a lake several hours out in the mountains and pretty isolated except for a few rich people who lived up there. Place was, and I shit you not, infested with Sasquatches.

Every 4th of July I would go up there to watch the rich people light off their fireworks and immediately after, I had found a logging trail that a large group of them would gather with their babies and all. I think to watch the fireworks. They'd let me get a little bit closer every year until my family sold the cabin. The last time I went there I took a couple friends and they chased us out of the forest until a car's headlights scared them off... That's also the most scared I've ever been.

For obvious reasons I don't want to share the location of this lake..