Rat

Rats are minor enemies. They relatively easy to kill, and are found in many Zelda dungeons.

A Link to the Past
Rats first appeared in A Link to the Past, as early as Hyrule Castle. They are simple enemies that don't pose much of a threat and can be defeated by any weapon in Link's arsenal.

The Wind Waker
In The Wind Waker, the rats quite often live in small mouse-holes in the walls. If Link gave them All-Purpose Bait, they would share some of their treasure with him; if he didn't, however, they would ram into him, knocking several Rupees out of his wallet, which they would then snatch up. In The Wind Waker, the bomb-carrying rats are simply referred to as Bombchu, as opposed to Majora's Mask where they were known as Real Bombchu.

Twilight Princess
The rats found in Twilight Princess have a more feral look to them. There are three distinct variations found within the game. The standard rats are black and are usually found in cellars and in Arbiter's Grounds feeding off of skulls. There is also a Twilight version of the rat called Shadow Vermin, which have a somewhat squid-like appearance. It is shown that both of these variations can swim.

The third kind are undead rats known as Ghoul Rats, which are also mostly found in Arbiter's Grounds. These ghostly rats cling onto Link and make him move very slowly, and prevent him from jumping off of the edges of a platform. When they cling onto Link as a wolf, Midna will squirm around wildly. The ghoul rats can only be seen and destroyed when using Link's wolf senses. A spin attack can be used to remove them off of Link.

Phantom Hourglass
Rats in Phantom Hourglass, much like their The Wind Waker counterparts, use mouse-holes to hide in, only this time they will run in one hole and out another as opposed to using the same hole. Some rats hold Small Keys which must be taken from them in order to proceed through the game.