Like not some shit you saw on the internet half-ironically, but something an actual flesh and blood human said to your face in a real physical space.
I'll start. I was working a service job and I had just finished helping this dude find what he was looking for. Seemed like a normal middle aged guy. After I showed him the product he need he looked me dead in the eyes and went "you know kid all the National Parks have secret bases in them." I just nodded, at first figuring maybe this was some actual real shit, like it wouldn't surprise me if the US military actually did hide some hardware or whatever in the National Parks. "They're filled with Samurai", uh, okay? "You see Japan actually won WWII, no bombs were ever dropped. And now the Samurai have secret radio bases in every National Park, Alcatraz is their headquarters." I decide to just fucking leave at this point and race walk to the back of the store and hide in the managers office. Apparently the dude spent 15 minutes wandering the store looking for me and asking my coworkers where I had gone.
I once spoke to a woman who thought that she was the reincarnation of a famous pharao and because of this the secret police had kidnapped her to build a computer based on her brain, which they had scanned. The fascinating thing about it was that she was pretty clear that she was now out of danger. The secret police had treated her reasonably well, and they were certainly not going to kidnap her again now that they had their brain scan.