Was Snape Draco's Godfather?
This is a question that has been asked a lot, primarily because Sirius is Harry's Godfather. Snape was probably Lucius's best friend, just like Sirius was James's best friend, so it would make a lot of sense. I mean, I can totally imagine Lucius and Narcissa asking Snape to be the Godfather of their son, and that may be why Draco seems to be his favorite student. However, that may just be because he's the son of an old friend as well as a Slytherin (plus, he hates Harry a lot). And if you read my fanfiction, you'll notice that I'm completely contradicting myself, but whatever.
But then again, if Snape was Draco's Godfather, that probably would have been mentioned in HBP when Narcissa is asking him to protect Draco. Most likely, actually. Plus, it's likely that people only think this is true because that's the way it is in a lot of fanfiction.
So, as far as my own opinion goes, I think that they asked him to be the Godfather, but he refused, not wanting any sort of obligation to protect Draco in the future.