I think I rented that same video.cmwright1981: I rented a really cheesy how-to halloween DVD not too long ago. The one thing they showed that was cool was a chainsaw madman that made sparks.
I don't remember the entire setup, but basically it mimicked your Freddy idea. The chainsaw was outfitted with a replacement metal bar without a chain. There was one battery connection made to this fake bar, and the other battery connection was to a metal fence. Every time he revved up the chainsaw, he'd drag the bar across the fence and the sparks would fly. Pretty cool effect.
That is the only way that I have seen it done and as long as a car battery charger is used and not the battery itself it is safe. You do still want some space between the sparks and the TOTs.Did this one year in a haunted house with a car battery charger. Hung a large metal screen 9(2'x3') along the back wall and attached the Neg clip of the battery charger for it. Then attached a large metal bolt to the Pos clip of the charger. To make sparks, I just have to swipe the bolt across the metal screen. Don't know how real safe it was, but it was really cool!!! No one got hurt as we kept the guest more than and arms reach from the screen.