Orson Scott Card has turned out some dark fantasy that's not bad; Charles de Lint writes dark fantasy/horror under the name Samuel Key; Silverberg's odd novels with everyone from Merlin to Dracula in them might qualify as well, along with Chelsea Quinn Yarbro's Saint Germain novels--despite a vampire main character and a lot of angst, the flavor is still more historical fantasy than horror. The flipside of dark fantasy is more traditional fantasy novels that have a strong horror element, such as the Black Company books by Glen Cook or about anything by Tanith Lee. One might count the old TSR Ravensloft novels among these, or one might refuse to acknowledge their existence.