This is a great prank! I've gotten a few people with this, it is hilarious! You need a pyramid of bowling balls. I built mine over a period of a several years, collecting bowling balls here and there for free. The first layer of balls is buried halfway so they don't roll out from under, and the rest are just stacked up. I love the bowling ball pyramid.
So now everyone knows you have a bowling ball pyramid, you've had it awhile, you even have some extra bowling balls to kick around the yard. (we tried Big Croquet, but a sledgehammer doesn't move a bowling ball very far at all, and it hurts!)
You and some friends are standin' out in the yard, smokin' and jokin', and you casually roll one of your extra bowling balls down the sidewalk, so it bonks into the steps, or into another ball, with a loud klunk. You make a remark about how heavy they are. "What are these, like 16 pounds?" You stroll over to the pyramid (make sure your victim is watching you, talk to him about anything, so he watches you) You pick up the top ball off the pyramid, obviously it is very heavy, as he sees you strain to pick it up, and make an effort to toss it a few inches into the air and catch it again, with a grunt. Then you push THROW IT AT HIM with both hands, oof!
The word "priceless" can only begin to describe the reaction. The look of shock as the bowling ball leaves your hands, headed toward him. The moment lasts seems to last forever. Imagine what goes through his mind!
That's when they learn, that yesterday you replaced the topmost bowling ball with your son's black rubber kickball that very much looks like a bowling ball! What a hoot!