I'd definitely have to say my favourite King was also the Gunslinger series... although I've only read the first three (3rd released while I was in high school).
There is one book though that I've been racking my brain to remember the title, and after enough searching I finally found it.
The Long Walk - published as Richard Bachman.
Most books are way better as books then movies.
And then some books, like this, have little hidden discoveries that can only be hidden if the story is told/read (and not viewed). This was one of them. I loved it. I remember how insanely shocked I was when a key ticket was explained. So... this will go down as my 2nd fave King of all-time.