WordNet sense 1 (a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn):

trafficator, turn indicator, turn signal

WordNet sense 2 (blind consisting of a leather eyepatch sewn to the side of the halter that prevents a horse from seeing something on either side):

blinder, winker

WordNet sense 3 (a light that flashes on and off; used as a signal or to send messages):

flasher