Being scared by a customer!! –
Last year when I worked at SCarowinds, I would hide in places which weren't necessarily actual hiding spots. One of which was behind a wall that was hinged so it acted like a door. I decided to hide behind the wall with it pushed out a bit so as the customers came down the hall, they would just think it was a wall at an angle and I'd jump out. I had to prop my foot at the base of the wall because a lot of customers tried to push the wall because it was a rather tight squeeze between the path and the wall. This was a VERY effective scare for the most part because most people just thought it was a wall and I'd bang on it and jump out. Well there was one customer who I'll assume had been through the house and so he decided to jump behind the wall before I could pop out and he startled me! I have to admit, being a character in a haunted house and getting scared by a guest is pretty darn embarrassing!!