Móði and Magni
Thor hit the giant Hrungnir in the head with his hammer, Mjölnir, shattering Hrungnir's skull. The giant then fell dead, as his leg landed on Thor's neck, pinning the god to the ground. The other Æsir tried to lift Hrungnir's leg off of Thor, but were unsuccessful. Thor's son, Magni, who was only three days old at the time, then came to his father and lifted Hrungnir's leg off of Thor all by himself. In his gratitude, Thor gifted his son Hrungnir's horse, Gullfaxi (Old Norse: "Gold-mane"). Odin himself was upset that Thor gave the horse to "the son of a giantess" and not to Odin, Thor's own father.