You could make crazy DIY Halloween decorations to scare the creeps out of trick or treaters in your neighbourhood. You could dress up drones as flying ghosts or ghoulish goblins to strike fear into child-sized candy beggars. You could be the cranky old man who turns his light off and seeps scare by ignoring costume wearers.
Or you could make your own PVC air cannon that could shoot out candy, flour, scary flying Halloween objectiles or whatever the heck you want to freak out (and maybe accidentally hurt?) anybody who dares come your way. [Household Hacker]