Octorok

Pic found by Krisi

The Octorok is perhaps as much part of the Legend of Zelda as Link or Zelda, having appeared in every Zelda game. It's an octopus, shooting rocks from it's snout. In the 2D Zelda games, they seem to have adapted to living on land, and can generally be killed with one or two hits from the sword. In the 3D Zelda's, they live in the water, and can be killed in a number of ways, the most common being using your shield to reflect the rocks they spit at you back at them, though they can be killed with any projectile as well. In Majora's Mask, shooting an ice arrow at them will make them platforms.