As teenagers, some friends and I had a very surreal experience in the graveyard of a closed down mental asylum. We even recorded it, but of course the videocamera was lost/stolen when a friend moved. Huge wall of text below, but I swear that this actually happened, not joking whatsoever.
Anyway here's the story. A friend had one of those energy crystals attached to a chain, it starts revolving when it "senses energy." When he demonstrated to us how it worked I was very skeptical but I really couldn't explain it. He dangles it with his index finger and thumb and it sits still but as soon as you put your hand beneath it it starts revolving. From what we could tell he didn't move his fingers at all. Anyway, we decide to go to the infamous mental hospital in the area which had a graveyard up on a hill behind it to test it out.
We all sneak up to this creepy graveyard under the moonlight and just walk around for a bit looking at the white cross graves and memorial statue in the middle. After a few minutes of hyping eachother up with hypotheticals of conjuring zombies by accident, we turn on the camera and my friend takes out his crystal.
The group of us surrounded my friend as he outstretched his arm with the crystal dangling from his fingers - it was completely still. We waited for a minute before deciding to walk around slowly trying to find a ghost. I tried to keep looking at the crystal but my mind got the best of me and I had to keep looking to the woods to make sure we weren't attacked by whatever would be hiding in the woods of an abandoned graveyard. I lost interest pretty quickly because I don't believe in the paranormal so I was just reading headstones and looking at the moon.
I don't recall how long they walked in circles with nothing happening. Then it happened, all of them just started freaking out shouting at my friend to stop fucking around. I run over to see what they were yelling about when I look down and see the crystal spinning wildly. The friend holding the crystal kept shouting "Look at my fingers! They're not fucking moving!" And they weren't, he had it gripped tightly so there's no way he was causing it to revolve so fast while he was stationary.
The group of us just stood there in awe, no explanation. After about 2 minutes, the friend holding crystal asks "if there's someone here, stop the crystal." The crystal stops immediately, like someone just grabbed the bottom of it, no fucking joke. At this point we all shit our pants, jumping up and down, yelling to stop fucking with us etc. But the friend with the crystal calms us down and says it's starting to move again.
Same thing as before, believe me I inspected everything, his arm was still and his fingers weren't moving at all. This time he asks if the spirit is still with us to start spinning the crystal the other way. Sure enough it slows down and starts to wiggle in the opposite direction. At this point I didn't want to go on, it was getting too real for me. But they decided they wanted to find where the fucking thing lives.
My friend asks "it" if its grave is here, can it lead us to it? So with his outstretched arm he moves to the left, and the crystal stops moving, moves to the right and it started to spin again. So here we are using a crystal to find the grave where this thing lives, the friend with the camera keep close watch on everything the crstal was doing, stopping...spinning...stopping....spinning etc.
Eventually they're right in front of a stone, white cross tombstone when my friend shouts "this is it!" We all gather around the grave, and I swear to God, what does the friend with the crystal tell us? "That's my mother's maiden name."
Like I said, I swear that I did not make any of this up. My friend might have just been screwing with us, but that was single handily the most unsettling thing I ever witnessed.
TL;DR With the use of an "energy crystal" my friend discovered a possible relative was trying to contact us from beyond the grave.