SIGURD & THE DRAGON FAFNIR
Origin: Norse Myth
Sigurd (also known as Siegfried) Volsung was told by the dwarf Regin to gain fame and power to slay a terrible dragon named Fafnir that guarded a huge mound of treasure.
Sigurd took up interest in this dragon, and recently was awarded with his father's broken sword (named Gram) which Regin forged back into one whole massive sword. Sigurd and the dwarf rode to find the fearless beast. What Sigurd did not know is that Regin's brother murdered their father to gain the wealth of the kingdom. This brother's name was Fafnir. Fafnir, because of his greed for gold and jewels changed his corrupt self into a massive dragon to protect his hoard better.

From what Sigurd knew of dragons, their tough,scaly hide on the top of the body was impregnable to any weapon. Regin suggested building a pit in which Sigurd could hide. So they both dug a pit outside of the dragon's lair. With Sigurd hiding, Regin covered the pit with branches. He waited hours for the dragon to come back from its daily visit to the watering hole nearby. Finally, a shadow covered the top of the pit, and Sigurd took the huge sword Gram in both hands and shoved as hard as he could up towards the exposed, soft belly of the dragon. With the dragon dead, Sigurd climbed out of his hiding place.

Regin then caved out the beast's heart to roast. When handing it to Sigurd to share, he burnt his hand and sucked on his fingers. Moments later he heard chattering, and surprised, looked up to see birds talking. They were saying how the dwarf was planning Sigurd's murder. He saw the truth in the dwarf's eyes and took out the sword and sliced off Regin's head. He went into the cave to claim the treasure as his own.
To learn more, look at <a href=”http://www.pitt.edu/~dash/sigurdstone.html”>The Sigurd Runestone</a>

Source: http://www.draconian.com/history/history.htm