Gungnir is part of the hallowed set of weaponry and is the fourth highest-tier spear in the game, next to the Mushroom Spear, North Pole and (on the console version) Tonbogiri. It has a base range of 12 blocks (this cannot be increased with prefixes that increase size). It provides light in very similar way to the Dark Lance and the Mushroom Spear`s glowing mushrooms..
Gungnir's large size, long reach and the bright light particles it emits make it the perfect tool to check the presence of caves, ores and treasures through walls.
Gungnir, and in fact all Spears, cannot be reforged with the Legendary prefix as of 1.1.1, due to them not supporting prefixes that increase size.