One way to scare the trick or treaters in your neighborhood would be to cover your house or yard with glow in the dark decorations! Rust-Oleum has glow in the dark paint that works on wood, metal, or plastic.
If you had some old faded decorations that were still in good shape, painting them with glow in the dark paint would be an easy way to keep using them. Of course, you could cut out your own spooky shapes and paint those as well! Or paint tombstones in your yard with glowing writing, or add some glow to your costume . . . there’s probably a hundred different things you could do with this stuff!
Anyway – it’s just an idea for your Halloween decorations or haunted house!