Gag
Gags are very commonly seen in BDSM and bondage fantasy. Many different items can be used, ranging from a hand simply clamped over the victim's mouth, to a scarf tied between the jaws, to adhesive tape placed over the mouth and face to seal the lips. There are also many kinds of specially-made gags, which usually strap around or behind the head. Special gags of that kind are usually made from leather or rubber.