UK: Insult used in the military when a recruit is either accident prone, clumsy, just plain slow or a combination of these.
PRIVATE you have left your safety catch of AGAIN...YOU ARE A SLOB, you are about as much use as a fekin' CHOCOLATE TEAPOT!, etc, etc....
UK: A chocolate teapot is an utterly useless item. Alternative terms also used are chocolate fireguard and chocolate kettle.
Refering to a useless or pointless item /deed /action /incapable person: "as much use as a chocolate teapot"