Weasley's Wizard Wheezes

Anti Gravity Hats
Anti Gravity Hats are a product sold at Weasley's Wizard Wheezes in Diagon Alley. A slogan written on the package reads "Ruin a gentleman's day by making his hat fly away!", so, the hats are supposed to be used as a prank. The Anti-Gravity Hat trick has been around for generations in the Wizarding World, and the are not to be used on Muggles.