I don't have one but have used one.
Was a school excursion to Canberra in Yr 9 so was around 14yrs. One of the girls made one out of paper and we used a glass. All of us thought "how fun!" "what a load of garble" etc it wasn't until the glass moved when no-one had spoken aloud and only 2 people had 2 fingers on that the room got quiet. I had a turn with my finger on the glass and it was amazing and scary to feel the thing move by itself! Especially when you know you're not pushing and it leaves your finger behind! The girl who was running it, did it quite often, she spoke to her dead brother and grandfather. Was the only occasion I have had but I will never forget!