I'm not much help, so will ask my niece and nephews for ideas...

Once was at a theater that was trying to convince us that treated lab rats had escaped into the audience. (Why? I don't remember.) They'd set up thin fibers (fiber optics? fishing line?) and blew compressed air at ankle heighth to have them hit our ankles as if they were rampaging rats. Not sure if this is practical or cost effective, though. (But tiny pairs of red lights zooming at ankles sends shivers up my spine...)

Letters from the govrnment, especially the IRS, freak me out. Clowns and porclein dolls... I imagine you've also done the sonic combination to frighten people just about annually.

I'll ponder and get back to you...