http://en.wikipedia.org/wiki/Javelin#Norse_mythology
In Norse mythology, Odin, the chief god, carried a javelin or spear called Gungnir. It had the property of always finding its mark (“the spear never stopped in its thrust”).[10] During the final conflict of Ragnarok between the gods and giants, Odin will use Gungnir to attack the wolf Fenrir before being devoured by him.[11]
…Odin also wounded himself with a spear while hanging from Yggdrasil the World Tree in his ritual quest for knowledge [14] but in neither case is the weapon referred to specifically as Gungnir.
When the god Baldr began to have prophetic dreams of his own death, his mother Frigg extracted an oath from all things in nature not to harm him. However, she neglected the mistletoe thinking it was too young to make, let alone respect, such a solemn vow. When Loki learned of this weakness he had a javelin or dart made from one of its branches and tricked Hod, the blind god, into hurling it at Baldr and causing his death
