Boulder

More of an obstacle than an enemy, Boulders are simply rocks that fall in random patterns when Link is traveling 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.

The Legend of Zelda and A Link to the Past
In both the Legend of Zelda and A Link to the Past, Boulders fall from the Death Mountain region of Hyrule. They usually fall in unpredictable patterns and can be quite difficult to avoid.

Link's Awakening
Boulders make a similar appearance as they did in The Legend of Zelda and A Link to the Past. While there is no Death Mountain in Link's Awakening, as Link makes his way to Turtle Rock, he travels through some caves and mountains, where he will have to dodge boulders falling from the top of the mountain.

Ocarina of Time
Within Ocarina of Time, Boulders appear much larger than the did in any of the previous Zelda titles. Picture to the left, this giant boulder is encountered within Kokiri Forest as Link tries to find the Kokiri Sword.

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!"

Oracle of Ages
In the Oracle of Ages, boulders appear on Restoration Wall. They can be quite tricky to avoid, and they can not be defeated.