I have a few incidents to relate, but the scariest was when I was about 20. My girlfriend was moving out of her family home, and moving in with me, so we went to her house to get her things. I'd never been there before...or since.
About half an hour after we got there, I started feeling like we weren't alone. It seemed pretty casual and harmless, and I told her, "There's something else here."
She looked a little concerned, and asked what I meant, so I said, "There's something here with us."
She turned pale and started telling me about all the strange things that happened in that house, from green marks constantly reappearing on the walls to the fact that she'd always find her Ouija board (She was an only child.) someplace other than where she left it...Strange places. like the back of one of her drawers to under her bed. There was one day when she was in the basement with a friend, and she heard her mother come home and walk down the hall to her bedroom. When she didn't answer her calls, she went upstairs and checked her mother's room, to see the edge of the bed looking as if someone were sitting on it...Then stood up as she was watching. There are other things, but back to my experience:
As time went by, the feeling I had started growing, and feeling more and more malicious, until I finally said, "I'm getting really uncomfortable. We need to go, now." As that last word left my lips, the overhead garage door opened about 2 feet and closed again.
Needless to say, we were gone in seconds.