I had a couple of experiences that, though not bad, freaked me out enough to stop using it.
I was in my Junior year in College, and lived in a small rented house by myself. I had a standard (Parker Bros.) Ouija Board, and read extensively about the occult at that time. I would regularly invite friends over, we would all get drunk, and play the Ouija in a dark room with a single candle in the middle of the table - we supposedly contacted many spirits, especially child spirits, during those sessions. Then one night, the Oracle moved too quickly for any one of us to decipher the text - we decided that one of us four players was messing around, and called it a night. I put the Ouija Board back in its box, and stuck it on the bookshelf. We continued drinking late into the night, before my friends left, and I staggered to bed.
Day 1] When I woke up the next morning, I found the Ouija Box on my bedside table, not on the bookshelf. I had been drunk, so I surmised that I may have grabbed it on my way to bed the previous night. I put it back on the bookshelf.
Day 2] We had a test coming up, so I drank only coffee (no alcohol) and studied all day. Fell asleep on the couch with my books and articles open all around me on the floor. When I woke up, the Ouija Box was on the floor by my hand, lying on top of all my books and articles scattered on the carpet. I remember wondering if I was sleep-walking in my exhausion, but I had fallen asleep with my tennis shoes on with mud on the soles, and none of the books or articles, nor the carpet, had any mud-marks on them. I stuck the Box back on the bookshelf, before I left for classes.
Day 3] The previous day, I had come home from classes exhausted with little sleep, kicked off my shoes, hungrily eaten a Big Mac, Ramen noodles, and fries for dinner, and collapsed on my bed in need of sleep - no time for coffee, alcohol, or anything other than a glass of Coke (Coca Cola) for lunch. When I woke up in the morning, the Ouija box was lying OPEN on the bed next to me, with the board half-open because the Oracle was stuck inside the board. That was when I started to freak a bit -- I was worried that I was sleep-walking and would get hit by a car or something. I put in back on the bookshelf before going to class, and resolved to eat only healthy foods and no caffeine or alcohol today.
Day 4] When I woke up in bed, the Ouija Box was next to me on the bed again, OPEN, with the board out of the box, the board OPEN this time, with the Oracle next to it -- but there was a new twist. My copy of the book Necrominicon (an ancient book on Demonology from Babylonia,) was also sitting on my bed next to it, also OPENed to a page with an incantation for summoning a particular demon. It scared the crap outta me - I grabbed the Ouija stuff and the Book, stuffed them both in the garbage, and carried it out to the sidewalk for pickup that afternoon.
Day 4 Part 2] When I got home from classes that evening, I noticed 2 things - the Ouija Board and my copy of the Necrominicon lying on the sidewalk with some coffee grounds around them, with the rest of my garbage gone. My neighbor informed me that she saw a big raccoon chewing at my garbage earlier, dragging pieces of my garbage out of the bag. I was unbelieving - a raccoon in daylight, on the street? She said - 'I can only tell ya' what I saw from my kitchen...'
I took the Ouija Board and my copy of the Necrominicon from the sidewalk, carried them to the backyard, poured lighter fluid on them and burned them to crispy ashes. Then I carefully scooped up the ashes, and slowly poured them down a creek with fast-moving water.
I lived in that house for almost two years after that - didn't have a single unexplainable incident.
"O' the good Lord some giftie gie us,
To see oursel'es, as others see us..."
~ Robert Burns