Wow... That IS terrifying. Mine would probably be the time where I came home to get some things while being home alone and encountering what I thought was a ghost. I didn't turn any lights on in my flat... I thought I would be in and out. I went to the kitchen to get a glass of water to drink and you know that feeling you get when someone is watching you? That happened. Out of the corner of my eye I saw the two mirrors I have hanging on my wall. Pretty normal, I thought. In one of them I saw a black outline of someone. I feel the lightest touch on my neck and almost like someone just took a breath and released it ever so gently. I turned around and saw that black outline of a person.
The scariest part was being able to see the eyes. I've never been that scared in my life. As soon as I saw the eyes for just that second, I knew seeing what I saw wasn't good.
After that, I grabbed my backpack and left. Didn't grab what I needed to grab, just left. Couldn't come home after this for another week. When I walked out, looking up towards my bedroom mirror I saw the same black outline. I don't know if it was only that one time that this thing was in my house, but that encounter and the contact it had with me was more terrifying than anything.