Boulder

More of an obstacle than an enemy, Boulders are simply rocks that fall in random patterns when Link is travelling through certain mountainous regions of Hyrule. They can often be hard to predict and will inflict damage on Link if he comes in contact with them. They first appeared in The Legend of Zelda and reappeared in both A Link to the Past and The Minish Cap.

Quote from The Legend of Zelda: The Minish Cap Boulder figurine:

"Appears on Mount Crenel, etc. These huge boulders come crashing down from cliff walls. They fall in a random pattern, so watch your step!"