There are so many.
It depends on who you’re interested in for what sort of thing? I could never pick “just one” favorite author. This is such a typical paradigm that I dont’ subscribe to at all. There isn’t “just one” of anything. 
There are many favorite authors I have, for various reasons.
For a great story (she’s not the best writer, technically speaking) J.K. Rowling does an honest job of it. She tells some great stories. She could be a better writer, however.
Stephen King, obviously tells some amazing stories. His writing is better than average, and in some cases genius if you read enough of it to find out.
Dean Koontz tells some wonderful stories–the Odd Thomas stories are well done.
Steven Pressfield has written some great ones. I’m thinking of “The War of Art” and “The Legend of Bagger Vance” as well.
Chuck Palahniuk … say no more.
James Joyce…Aldous Huxley
Salman Rushdie! For the best in subversive writing…can’t go wrong with him. 
You get the idea.