Destroyer
The Destroyer was a magically powered Asgardian automaton, created by the Dwarves to guard Odin's Vault.
The Destroyer had no operating intelligence of its own, obeying the wielder of Gungnir without question. It could also be controlled directly by the wielder of the spear, or the magic of the spear could be used to see through its eyes, allowing the ruler of Asgard to safely view dangerous places or situations.
As well as being extremely strong and durable, the Destroyer was capable of firing energy beams from its 'face', and rearranging the metal plates which made up its body, allowing it to more quickly and easily attack targets behind it.
During Loki's brief reign as King of Asgard, he sent the Destroyer to Puente Antiguo to kill Thor. However Thor, Siff, the Warriors Three, and Tony Stark were able to defeat it.
The remains of the Destroyer were used by S.H.I.E.L.D scientists to create energy weapons, one of which was used by Phil Coulson against Loki during the Chitauri Invasion, immediately before his death.