First, get bouncy balls, like the ones you get in quarter machines, and put them on the ground next to a ledge that drops off to a lower floor. At my mall its a three story drop. Then have someone watch from farther away while you walk past and just lightly kick the ball off the ledge. stay out of sight from the bottom floor and walk towards your spotter. they will have a pretty funny story to tell!!

As soon as some one enters an elevator and the doors close, press the button to get on and run away. they wont go any where and the doors will open and they will be dumbfounded.

the last prank is you get like 5 of your friends, the more the better,and find one of those stores that you have to be 18 to go in, like fancy electronics or the like. Send a person in, and the clerk will ask you to leave because you dont have a parent with you. after you leave keep sending in friends one at a time in quick succesion so that the clerk has to ask someone to leave every thirty seconds and gets really angry