Ocarina of Time
In Ocarina of Time, Torch Slugs can be found in the Fire Temple. These flaming puddles of goop have quite the personality. If they see Link, they'll relentlessly follow him around, jumping at him until he is out of reach. They can rack up quite a bit of damage, so Link must quickly use any attack he deem appropriate. Both making contact with the Torch Slug and being hit by its attack deal half a heart of damage.
If Link is catching them off guard, his sword can easily do the job. Otherwise, Deku Nuts are quite effective. Once they've been hit, their flame is extinguished, leaving them vulnerable and scared. Link must chase them down and smack away at them before their flame returns to defeat them. Once Link has acquired the Megaton Hammer, he can use it to hit the ground, flipping the Torch Slug and making them completely helpless.
Torch Slugs in Twilight Princess are of a smaller appearance than their Ocarnia of Time counterparts and are significantly weaker, as taking one strike from an arrow or sword defeats them. The slugs also appear on cave ceilings and drop when approached. They are found in three places: the Goron Mines, Lake Hylia Cavern, and the Cave of Ordeals.