These days, pennies are useless when it comes to buying things, and that's why Canada doesn't even have any anymore. But, there are a lot of cool things you can do with those worthless pennies, and what's better than a good old-fashioned prank?
If you live in a college dorm, military barracks, or similar structure, they have a huge heavy metal door with deadbolt lock. By binding bundles of pennies together with some duct tape and sticking them in the door frame of a locked door, you can prevent the door from unlocking and opening altogether, trapping your victim inside.
Just make sure you only do this on your roommate. Doing this to random people not a prank, it's just mean. Revenge is what pranks are made for.