Armos Knights

The Armos Knights guard the Pendant of Courage in the first dungeon of A Link to the Past.

Three arrows (one if you have Silver Arrows) destroy one. But they can also be defeated by hitting them with the sword. Once only one is left, that one will turn red and try to squash Link. After it is defeated, Link gets the Pendant of Courage and a Heart Container.

Later in the Ganon's Tower they guard the way up.