Every year my middle son and his friend like to dress up as some monster or other, sit quietly on the front porch as if they're simply part of the decor and then scare the trick-or-treaters. Come on - you've done that, too!
Everyone EXPECTS that, though. Any scarecrow, mummy, ghost, or zombie sitting by the front door is simply anticipated to be something that will jump out and get you.
If you want to do something different this year, ditch the fake body routine and go for something as innocent as a metal garbage can.
Take a look at the reactions here:
Now, that's the kind of response you want to get, right? The screams, jumps, and then the nervous laughter when the kids realize what's happened.
One way to do this is to rig the lid with some fishing line that you pull when people pass by. If you have large groups of people who come pretty quickly through your street you might want to rig a few different items so that you can scare a few crowds in a row before setting everything back into place.
Just make sure you're very careful about where your line is running - no tripping people as they're running to or from your house! We don't want to hurt anyone. I always find a good few practice runs are in order.