Octorok

The Octorok is perhaps as much part of the Legend of Zelda as Link or Zelda, having appeared in every Zelda game except Twilight Princess. It's an octopus that shoots rocks from its 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. That makes them as "normal enemies". In the 3D Zeldas, 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. However, they can be killed with any projectile as well. In Majora's Mask, shooting an ice arrow at them will make them into platforms. In The Minish Cap they appear in three forms: Blue, Red, and Gold. The blue ones are tougher then the red ones, but the gold are the toughest and can only be found by fusing kinstones. In The Legend of Zelda: The Wind Waker, Octoroks are squid-like creatures that shoot at you, as always. When out in the ocean, these creatures shoot bombs at you instead of their normal rocks. However, if you are going at a good speed, their attacks pose little to no threat.

Quote from The Legend of Zelda: The Minish Cap Octorok figurine: "Appears in various areas. There are red and blue ones. They've appeared in every Zelda game to date. They spit rocks, so be careful."

Note:

Twilight Princess is the very first game in the series in wich Octoroks are totally absent; the monsters that were thought to be octoroks in other locations are an entirely different species known as toadpolis. Although toadpolis act similarly to octoroks, they resemble developing tadpoles and they actually swin underneath the surface of the water. They are only found in a few place and there are smaller ones and larger ones.