everyone seems to interpret this as "the most disturbing"... I've read about some lesser-known diseases like fatal insomnia and prion disease, and got really into creepypastas (particularly sonic.exe and NES Godzilla) a while back, and to an extent computer malware could be considered disturbing, but I don't consider any of that to be odd, because a lot of people enjoy reading about disturbing things. (If they didn't, my YouTube recommendations wouldn't be flooded with poorly researched, clickbait video essays about things that are "disturbing" and "controversial".)

The most obscure rabbit holes I've been down include Bandcamp netlabels and software mascot lore.