Barker, easily. The six Books of Blood volumes are probably my favorite pieces in all of literature, and they also provided me with the template to work from for my own short stories. Of course, I worship at the altar of the other early shit (Cabal, Hellbound Heart and most especially The Damnation Game) as well. Also, I might be the only person I've heard from who liked Mister B. Gone...I found it funny as all hell, even when it got serious.
King I enjoy sometimes, but he becomes stale for me. IT, though, is one of the best books ever written.
I'm down with Lovecraft (at the mountains of madness, pickmans model, shadow over innsmouth) and Poe (the pit and the pendulum, masque of the red death, house of usher) as well.
I'm really into Laurell K. Hamilton. I'm not sure if she's really considered horror or more fantasy. She writes about vampires, lycanthropes, fey, and goblins. Just about every mythical creature you can come up with. Her main character in one series is a vampire executioner, who is also a necromancer. She also adds a bit of romance in there with racy sex.
Hey Rustin. Hot Zone was a great scary book eh? The fact that it's a true story makes it a really scary read.
Christopher Fowler is a great British author. I like the Texan style writing Joe R Lansdale and Richard Laymon (his Dreadful Tales are fab). I've read all of James Herbert's, recommend The Others (nothing to do with the Nicole Kidman film BTW).
As far as actual writing is concerned, very few can touch Ketchum's dialogue and characters (King being the obvious exception). I find a lot of horror writers are pretty lame authors who get off being gory (ie: most of Keene's stuff is pretty popcorn). A few other good ones:
A few of Bentley Little's novels (The Revelation, The Summoning), although he's got some shitty ones here and there.
But the king of unique horror has got to be Tom Piccirilli...go read A Choir of Ill Children and tell me it ain't some crazy shit. Poetic and totally bizarre, and one of my favorite authors of any genre.
"We're so precious, aren't we? Everyone's gotta live, everyone's gotta be happy. It's a joke. It's an absolute joke. Evan, that's what you didn't get. You think people are equal? They're not..