The way I liked to scare Trick-or-Treaters back in middle school was to create a sense of safety by establishing a "scarecrow". As neighbors approach, they are likely to assume there is a man inside the costume, waiting to jump out at them. We create a false sense of security by having the scarecrow drop the sickle and not pick it up. Then they go to the door for their candy, with their new found sense of safety and when they return, he is holding the sickle once again. Just before they put it all together... he strikes!

My cousin Paul is the scarecrow in this video but my brother and friend Dave have played the role in other years.