Cambion

Cambions, according to show's myth arc, are the offspring of demons by human mothers. They are also known as Catagos (sp?) or the Anti-Christ. In reference to the Anti-Christ being the son of Satan, the Bible, according to Castiel, is wrong, and the Anti-Christ is not the son of Lucifer, but merely demon spawn born of humans. This lineage makes them incredibly powerful and capable of "killing the Host of Heaven with one word."

Other references to Cambion can be found here http://en.wikipedia.org/wiki/Cambion.

A famous cambion is Caliban from Shakespeare's "The Tempest".

The mage of the King Arthur stories, Merlin, is also often said to be half human and half demon, and was original intended to be the Antichrist.