I was actually in a haunted house with my Mother and my Aunt when I was about 6 or 7. Of course, they were too scared so I had to be in front guiding through the pitch dark haunted house and whenever those bastards in creepy costumes would pop out and scream, I believe I shit a couple of times. Based on my memory right now, that's the most scared I've ever been.
I've had a couple of nightmares a long time ago and I woke up and my heart was racing (forgot what they were about but I'll never forget that I had them) but that's pretty much it.
Also, do movies count? I guess they do. When I first saw Insidious. I watched it with my Mother in the living room, at night, around 10pm. No lights. Let's just say, I might have shat a few more times. I got legit freaked out watching that movie. Especially in the dark.