« Ta gueule ! »
“Shut your trap !”
Variation: « La ferme ! », which is a frozen expression. La stands in for gueule.
Note: For “Ta gueule !”, ferme (close, shut) is understood, so there’s no need to say it. Also, gueule means mouth, but that of an animal. (Muzzle, snout, maw, etc.) This expression is rarely ever said jokingly.