I honestly believe that ghosts exist. I have a creepy story to tell too.
One night, I was having a sleepover with my friends. All of a sudden we saw this freaky, gingerbreadman shaped thing FLOAT (Thats right, FLOAT!) across the doorway. We were scared silly. And we ALL saw it. 5 girls saw the EXACT same thing. And it started smelling like muffins after too...
I don't know what it was, but all of us think that it was a ghost. Yes, ghosts don't look like gingerbreadmen. But still, it could have been! I might try to draw a picture of it on paint later. It's not going to be easy though...
But even if that didn't happen, I would still believe ghosts exist. I don't know why, but I just think they do. It's like something that your brain tells you, and personally you (and sometimes only you) know that it's true. You don't know why it is, or how you came to that answer, but you just know it, somehow.