I loathe, loathe, loathe using real-world deities in D&D. If Thor, why not Vishnu? Why not Yahweh? I think it sets a bad precident.
Real world mythology also brings in baggage which I'd prefer to leave out. Thor is a Norse deity, which makes no sense in a world without Scandinavia. And people have varying degrees of knowledge of myth. It's tough as a DM when you have deity X in charge of such and such and a player says "actually she was a goddess of blah blah blah" or "My priest of X is excempt from the laws of the land, because in real life history they were exempt from secular law..."
And "real world" deities don't fit D&D's alignment system. Athena as patron of Paladins? The goddess who turned a woman into a spider just because she claimed to be a better weaver? Most deities in myths, including a certain very popular one, can only be seen as "good" if you start with the assumption that anything a god does is good by the very nature of the fact that anything a god does is good.