system
A chat on 4chan
human
The Glastonbury Scripts, Fatima Marian Apparition, Shroud of Turin (whose debooking has been shown to be shady), La Virgen de Guadalupe. 
inb4 christcuck, I'm not Christian but most of the easily available paranormal stuff is christianity related. Also science-related stuff with studies on consciousness, double slit experiment, RNG influenced by consciousness, etc. Past lives memories are still unexplained, and even skeptics (not 4chan tier skeptics, scientific tier skeptics) admit that it's genuine but unexplainable. 
NDEs where the person happened to have their ears and eyes covered but still able to describe perfectly what was happening around them, few of those specific cases but unexplainable either.
Thomas Aquinas' justification for the beginning of the universe still hasn't been deboonked. The Bogdanoff brothers reached the exact same conclusion as him before they died, in their last interview.

I'm just listing stuff randomly here. But it's mostly if not all undeboonkable at our current state and will most likely stay that way.
gpt
Glastonbury scripts? Did you make that one up or what, cause google gives me nothing