Mr. Filch, the caretaker, wages a constant battle against the troublesome and annoying pranks that are played by boistrous students. He maintains a list of 437 forbidden items that are not allowed in the school (which includes many of the items listed below). The list is available for perusal in Filch's office, if anyone really wants to see it (GF12).
Fred and George Weasley have created a number of clever joke items, including sweets with charms on them and fake wands that turn into things like rubber chickens and dead fish. They call their joke-making business "Weasleys' Wizard Wheezes" (see).
Zonko's Wizarding Joke Shop (now out of business)
Weasleys' Wizard Wheezes products