Their only use is to zoom in and view far away places. They are superior to the Sniper Rifle for simple viewing, as their view is uncluttered by cross hairs. This item is first used during the mission "Leap and Bound".
Due to a glitch in Grand Theft Auto Vice City Stories, if the player presses the attack button while equipped with the binoculars, Victor Vance will start punching the air and if that is done in front of a pedestrian, his hands will just go through the pedestrian's body and not actually do any damage.
Looking through the binoculars in Grand Theft Auto: Vice City Stories.
Playboy X using binoculars in Grand Theft Auto IV.