Trick Wands are joke objects created by Fred and George Weasley and sold by Weasleys' Wizard Wheezes. These wands appear normal in every way, but when used to cast a spell, they turn into random objects (e.g. rubber bird). A more expensive version beats the user around the head and neck.
Mrs Weasley gets very frustrated when she picks a stray one of these up even though she'd banned them from the house. Also, Ludo Bagman finds these very amusing and offers to pay 5 Galleons for one at the Quidditch World Cup.