A few years ago as I was standing beside the front door watching the next group enter the house one young man mumbled under his breath,"I'm gunna Kill one of those SOB's!"
He had been arguing in the parking lot with some people who happened to also be included in the group coming in the house.
I never took my eyes from him for the first two rooms. He never smiled , never talked to anyone else , looked very serious and never took his one hand out of his pocket.
The Police surrounded him and handled that situation rather well. I think he was surprised we were paying that much attention to him too.
When surounded by uniforms he really still had to work at faking a smile, he resisted emptying his pockets but eventually did.

The frightfull trick here is to seem as if you are right in their face yet not be availble for those quick dental adjustments or a painfull nose-flattening.
I do this many different ways, mixing it up so the customer/victim is off balance and will not be anticipating the next upcoming scary confrontation.
This is not really so hard to do when a tour here almost always runs 90 minutes.
Plenty of time between such events to lull almost anyone. And of course this also usually allows me to spread the fun around from front to back, middle, newbie, returning patron who even though they have seen the scare before might not know I have more than one way to effect it in a given location.
I love it when the returning patron acts so smug then is the first one genuinely screaming!