This is a fascinating thread. I think a lot of frightening experiences among JWs are a direct result of being constantly brainwashed into believing that anything outside the safe realm of the Watchtower Society is under the influence of Satan and second hand items were most probably posessed by demons. I can remember personally throwing things away that had been given to me just in case.
On one occasion I had been given some make-up by a colleague at work. The lady had told us she was a Spiritualist but she seemed nice enough and the make-up was brand new and good quality so it seemed a shame to refuse it. However, that night I woke up feeling as though my bed was being shaken and I was terrified. I can remember doing what we were told to do in those circumstances and shouted out "in the name of Jehovah go away". The shaking stopped and I eventually went back to sleep. The make-up was disposed of at the first opportunity. However, did that really happen or was it just my vivid imagination working overtime? In retrospect I am inclined to think it was the latter.
However, I would never for a second ridicule or disbelieve anyone claiming to have had a bad experience, especially if several members of the family experienced it together which must have been very frightening and unnerving. It makes me think there may be powers beyond what we know, but not necessarily demonic. Some kind of quantum energy perhaps?
Just out of interest, over the last few years I have helped out working in antique centres packed with all things imaginable, often spending many hours alone amongst them, but never once experienced anything unusual.