Heimdall (meaning Light-Shinning) was the golden toothed, far-sighted watchman of the Vanir. He wore simple clothing, but could see like a hawk, and his golden teeth glittered in the sun whenever he laughed. He was one of the flightiest of gods. He will die at Ragnarok fighting Loki the wily. On the Poetic Edda, in the Lay of Rig, Heimdall is depicted as been the father of mankind.
Heimdall was the asgardian god guarding the Bifröst.
He had a horse called Gulltoppr ("Gold-Top") and the horn Gjallarhorn (meaning "Shrieking Horn"), with which he'll announce the beginning of Ragnarok.
He was the guardian of the rainbow bridge known as Bifrost (the only passage from Midgard to Asgard), where he watched the coming of the Jotunns or any other enemies that tried to invade Asgard.
He lived near the Bifrost, on the Himinbjorg ("Heaven's Cliffs").
Heimdall plays a major role in the 2011 film Thor. In the film he guards the Bifrost and protects Asgard from any treat that might cross the Bifrost. He has a some type of cosmic awareness, able to watch almost anything that occurs in the nine realms. He was portrayed by Idris Elba.