Aziraphale is a fictional angel in the novel Good Omens by Terry Pratchett and Neil Gaiman. He was supposedly the angel of the flaming sword who guarded the Garden of Eden after Adam and Eve were cast out.
In the novel, he gave his sword to Adam and Eve, as he thought they needed the fire. It is implied that it became the sword of the Apocalyptic horseperson War.
He went on to become Heaven's agent on Earth, under the guise of running a second-hand bookshop in Soho. He collects prophecies, especially apocalyptic ones, although he's aware of the steps that have been taken to ensure none of them are accurate.
He has a strong friendship with his opposite number, the demon Anthony Crowley. The two often meet up to compare notes, much like Cold War agents who find they have more in common with their immediate opponents than their distant superiors.
Concerning the character's name, Pratchett says "It was made up, but from real ingredients".