Using pliers, try to grip and pull the key straight out. If you can't get a grip with pliers or needle-nose pliers, cut off a coping saw blade and with the teeth pointed outward, insert the blade into the keyway and try to hook and drag the key out. As a last resort, remove the cylinder (see below). Insert a stiff wire into the cam slot at the back of the cylinder and push the key out. Or take the cylinder to a locksmith.