Smasher is the mini-boss of Face Shrine, the sixth dungeon in The Legend of Zelda: Link's Awakening. It appears to be a black and white sphere with one eye and an antenna protruding from its top. It also makes a sound resembling an animal.
Smasher's method of attack is to hurl a heavy ball at its opponents, trying to knock them down. Link, through the use of the Power Bracelet, is able to pick up the ball and throw it back at Smasher until it is destroyed. The ball can be 'blocked' by a hit from the sword, often to the advantage of the Link, who can then easily pick it up and throw it back without chasing Smasher to the grab.
Smasher's name originates from the word 'smash' because the large ball Smasher throws at Link is obviously intended to smash him.