For me, horror is a lot of fun, but sitting down to write it is a challenge in that your audience is jaded by things like slasher flicks and suspense. While I agree with Bastcat, that there are a limited number of scenarios, part of what I enjoy about writing is that you are forced to find a new spin on those concepts.
What has not been explored recently in fiction or even in film is the degredation of the human spirit as horror, which authors like Joseph Conrad seemed to understand and write so well. It goes a long way to displaying how there are many 'types' of horror, each with its own delicate flavors.