My wife took me over to her Mother's once, and we stayed the night. It's not an old house, but one that is maybe 30 years old young, as far as houses go. It's out in the country, and it doesn't have any story to it. It's just a small subdivision out in the country where each property has 2-3 acres for each house.
We went there, and I think we watched TV for a bit, and then started getting ready for bed. Out of the corner of my eye, I saw this guy walking down the hall, in a white T-shirt, and what looked to be dark pants. He went into the last room to the left, but I never saw his face. When I saw him, I knew we were the only ones in the house, so, I definitely questioned who the heck this guy was, and walked to the bedroom and turned the lights on. I saw nobody in there. I was so convinced I saw him, I looked through the closets and under the bed nothing.
I walked out, and apparently had this odd look on my face, because my wife asked me why I looked so funny. I told her what I saw, and how it freaked me out. The funny part is, after I told her, it was she that looked so stunned, not me. When I asked her why she looked so shocked now, she told me that both her and her Mother had seen that guy since she was a little girl. She said, like me, they always saw him out of the corner of their eyes, and he always did the same thing. Walking down the hallway, towards the back left room.
To make matters even stranger, she said they had one of those old TV's as well as old microwave. They both required you to "Click" things on, not an electronic switch. Even though it would take force to turn these things on, or change channels, thing would happen all the time that seemed to defy physics. The microwave would turn on, and the dial would twist to 5-10 minutes, with nothing in the microwave. The TV channels would CLICK over to the next channel. Over the years, instead of being afraid, they would just get annoyed and would tell him to stop it. Once they did, things would stop.
I never believed in ghosts before then, but that changes after you see one!