Mjölnir
In Norse mythology, Mjolnir (also Mjollnir, literally "that which smashes") is the Hammer of Thor, the god of lightning and thunder. This war hammer (made by Brok and Eitri) had enormous destructive capabilities, and was associated with lightning. When thrown, it would return to the thrower's hand after striking its target. Only Thor and his son, Magni, could lift it. The account of how Thor came by Mjolnir is given in the 11th century poem Thorsdrapa.
Thunder
To wield this formidable weapon, even a deity like Thor needed special iron gloves and a belt that doubled the wearer's strength. The strike of Mjolnir caused thunderclaps, and the name of this deity has produced the word for "thunder" in most Germanic languages.
Norse myth
With the hammer, Thor indulged in his favourite sport of killing giants. Most of the surviving myths centre on Thor's exploits, and this and inscriptions on monuments suggest that Thor was very much the favourite deity of ancient Scandinavians.
In Trymskvida, the most light and funny of all Thor's adventures, the giant Thrym secretly steals Mjolnir from Thor and then demands fair Freya in exchange.
Marvel Comics
In the Marvel Comics version of the character, the hammer could also allow Thor to fly by grasping the holding strap of his hammer after he threw it in the direction he wanted to go. It also allowed him to control the weather, travel through time and other dimensions. It could be used defensively by twirling it by its holding strap to deflect bullets. It had to stay in physical contact with Thor to prevent him from turning back into his mortal form of Doctor Don Blake after sixty seconds, but that weakness was removed after an alien warrior named Beta Ray Bill proved worthy of Mjolnir and received a variant hammer with the transform weakness being transferred to it.
Games
Mjolnir also appears as a magical artifact in the roguelike computer game NetHack and also in the Diablo-like "Darkstone".
In both Marathon, the main character is a cyborg whose type is named Mjolnir, and in Halo, the protagonist uses a combat suit designated as MJOLNIR.
In the Volition game Freespace 2, Mjolnir is a long range beam cannon.
In the Breath of Fire III game, Mjolnir is the most powerful thunder-elemental magic spell.
In the Quake expansion pack Scourge of Armagon, Mjolnir is reproduced somewhat faithfully as a hammer weapon which fires lightning bolts at nearby enemies when it is struck against the ground.