The magic spear of the god Odin, Gungnir (Old Norse "swaying one") always hits its mark and never misses its target.
In the Völuspá, the war between the Vanir and Aesir is officially started when Odin hurls a spear over the heads of the Vanir; whether this was specifically Gungnir or not is not stated.
In Sigrdrífumál, Sigrdrífa, a valkyrie, teaches the legendary hero Sigurd the magical application of runes. She tells Sigurd that, as well as on numerous other things, runes were carved on the tip of Gungnir.
The spear was forged by the dwarves known as the Sons of Ivaldi, under the mastery of the blacksmith dwarf Dvalin. The spear was obtained from the dwarves by Loki, as a partial reparation for cutting of Sif's hair. During Ragnarök, Odin will ide before the Einherjar (the Valiant Dead) wearing golden mail and will attack the great wolf Fenris with Gungnir, though the great wolf will eventually swallow the one-eyed god and kill him.
In Too Human, Baldur's favorite guns, a pair of glass pistols called Havoc and Malice are also called "the Marks of Gungnir" and were gifted to him by ODIN.