I'd have to say it's a toss-up between Steampunk and Weird West. Although, Science Fantasy seems weird, too.
For those of you who've never heard of those:
Steampunk--Generally, a subgenre of science fiction that focuses on Victorian-style technology. i.e. a computer powered by steam, a clockwork phone. etc.
Weird West--Think Cowboys and Aliens, and you get the idea.
Science fantasy--A hybrid of science fiction and fantasy. Star Wars is a popular science fantasy story. (Starships = science fiction. Force = fantasy.)
Steampunk and Weird West are odd but hardly the most peculiar. Then again, as a longtime reader of pulp fantasy, which is often pretty strange (try reading some Clark Ashton Smith) I may be a bit jaded where s-f & fantasy are concerned.
The whole transformation/furry thing is something I've long found peculiar. Stories in which characters, often self-inserts by the author, change bodies and have relationships (including sexual ones) with others who similarly transform. A late friend (who was a furry himself) edited a webzine of this stuff. They had an ongoing shared universe series about a world where a virus transformed people into animal forms. Even some of the columns were often written by the editors in their animal personae. Oddly, he did use a fair straight-up horror story that I wrote back in university, so it wasn't all furry stories but that seemed to be the lion-share of the material.
I think it's the one with the cannibal and the aliens.
Pooing through a tea leaf strainer, hoping to find the Lost City of Alantis.
incestuous scuba orgies at Lake Como
Some of the other erotica forums I've visisted, actually have a seperate genre dedidcated to pairings between human characters and various non-human monstrous beings (aliens, trolls, etc..)
blowjob-puke stories
manga-octopus sex
elephant-ant, May-December romances
Not really a genre of any note, but those sexual virgins who attempt to create erotic fiction, concocting all manner of acts which in reality are so far from the realm of plausibility.
We gotta create a genre for those.
The same GQP demanding we move on from January 6th, 2021 is still doing audits of the November 3rd, 2020 election.