I have a made up word I have never said to anyone.
Nobody claiming to be psychic has ever been able to detect it.
While it's a meaningless thing overall, it is endlessly entertaining to watch someone spiral from "trying" to discover it, to random guessing, to being angry and declaring that I'm lying and they got it the first time.
It's kinda like my secret. I have a secret I have never told anyone. It's another thing I will put before a self proclaimed psychic. Even once they progress to guessing, none have ever even thrown it out as an option.
And you'd be amazed how many self proclaimed psychics there are out in the world, and how many of them seem to really think they are psychic, to the degree that they'll accept someone presenting one or both of those challenges.
The made up word would be a difficult guess for sure. But my secret isn't something so rare that nobody could possibly hit on it as a guess.
I'm not willing to outright say that there's no thing that could be called psychic ability. What I am willing to say is that nobody has ever exhibited such, and likely never will