The freakiest thing that ever happened to me was a voice calling my name out of nothingness.
I was with my ex-grilfriend at the time, and we both agreed it sounded like my younger sister was calling me. I was in my room with the door closed watching TV my ex, when I heard my name called. It sounded like my sister was just outside my bedroom door. When I opened the door, to my astonishment nothing was there. I went to look for my sister to ask her what she wanted, and she said: huh?
I said: "Yeah, you just called me". I asked her if she was in her room the whole time, and she said yes. Her room is on the opposite side of my then parents' house. Suddenly, I was starting to feel very weird. I told my ex that my sis said she never called me. She was starting to freak out now.
It was pretty spooky.