[iamragmar]

There is a series from Eclipse and Pacific called Bernie Wrightson: Master of the Macabre. It was around 5 or 6 issues and it is absoloutely essential, it rerinted most of his artwork he did for black and white horror magazines in colour(sounds like sacrilage, but it is amazing colour).
The later issues of Scream, Psycho or Nightmare (all from Skywald) have some great stuff in them.
Creepy, Eerie and Vampirella have some of the most amazing experimental artwork seen in comics( but later issues could be extremely poor).
Twisted tales(which is filled with stories by Bruce Jones, who is in my opinion, the best horror comic writer ever)
Freakshow by Bruce Jones and Bernie Wrightson recently came out from Image and is brilliant.
You ought to atleast have some issues of Tales From the Crypt, Vault of Horror or Haunt of Fear( sometimes thet are a little repetitive, but having the best artwork ever makes up for it, they changed my life).
There is loads more but I think these are some of the best.