Regarding observations of things that are verifiably endangered, Frasier Fir https://www.inaturalist.org/taxa/136317-Abies-fraseri is, I think the only one I have checked off. Mostly because you have to climb a mountain in Appalachia to find any.
As far as least observations go (that isn’t a weird, hard to ID fungus) - maybe this little beetle? https://www.inaturalist.org/observations/114674025 its not a research grade obs yet but it seems to match the other recorded pictures - its just an absolutely itty bitty species (MAYBE 2-3mm long, tops) so I’m sure it gets overlooked.
In terms of observations, most likely the Gansu Leaf Warbler, which now only has 11 observations. Of course it helps that I am currently living in Gansu, and not many birders come here.
Though as for rare animals it wouls have to be the Crested Ibis, once thought to be extinct, but luckily due to a breeding programme in Yangxian (not too far from where I live), numbers are up.
The rarest taxon I’ve ever seen was almost certainly an insect that I did not pay any particular attention to.
Once we get out of large and / or charismatic organisms (vertebrates, orchids, cacti), it’s probably reasonable to assume that if we know how rare a taxon is, it’s not especially rare.
I don’t think so. Pretty sure they aren’t native, hence I said it was owned by someone or someone’s pet. Was “rare” because it became somewhat a rumor among the neighborhood.
The Diptera enthusiasts here might appreciate this:
Back in 2016, in a reserve in the northern Midlands region of South Africa, I came across this Small-headed Fly; it seems mine is the only observation of it anywhere in the world for iNat
Looks like a few observations for Acroceridae on iNat. Noticed there’s an observation from here in South Korea as well, putting the range up to at least three continents. Guess that’s something for me to keep an eye out for now. :)
An evening flying squirrel that ate bird food stuck to a patio door.
Once I am sitting on the edge of the lake suddenly a vision of America comes out of the water in front of me he jumps out of fear, returns to hide, then gets up again gets up curious looking at me.
The rarest for worldwide species I’ve seen would probably be the Kirtland’s Warbler and Piping Plover. Rarest for location seen might be this MacGillivray’s Warbler. https://www.inaturalist.org/observations/143815204