I built this last minute scare that for The Hex House. It is a fake bed with a hole in it for an actor. After the Wall-Walker scared guests they would be treated by someone lifting up through the mattress of a bed. I was surprised how effective this was. People recognized this effect from the movies and were terrified that it was now real and happening to them. If you have space I recommend doing this one.
The video for this is in my video section now. But here are some images when I was building it.