When I was younger, my parents used to dress up for Halloween. My dad would hide in the dark spaces of the lawn and jump out and scare kids. One year, he was dressed as a giant spider and the kids would drop their bags of candy and he had no choice but to go running after them, trying to give the candy back.
Carrying on the tradition, one year, my sister and I made this ghost kind of thing with a Halloween mask as a face. I laid on the roof and would drop it down when the trick or treaters came by to scare them. It worked, but no one dropped their candy.
Today, I was cruising the internet, looking for some unusual Halloween pranks and these are the ones I came up with.
From the Halloween-website:

In costume, knock on someone’s door and when they answer put candy into their bowl

One item on this list, I actually did as a kid–sign Christmas Carols when the people opened their door. But I also enjoyed moving the candy with a fishing line.

I like the last item on this list (particularly since I wrote a novel about disease)–go to work looking really sick and scratching a lot.

Happy Halloween! With or without the tricks!