A water balloon with a glow stick on the inside, in a stocking, hung from trees, patio cover, or the ceiling. Same pin elsewhere said: "Put a glow ball in a white stocking and hang many from trees or the ceiling." But what are glow balls?
Halloween creepy party punch, freeze water in a surgical glove for a scary ice cube. I've always liked this idea. You can also fill the glove with the punch so the ice doesn't water it down. Note: make sure NOT to use the powdered gloves.