Yes, I score for horror (although mostly radio and shorts).
Orchestral effects still work (scrapes, clusters, etc) but sound design is a far more modern sound. Pianos are still extremely effective.
Like a lot of modern scoring, horror music works well with pads and hits that sound indistinct and unrecognisable. i.e. create a vague floating harmonic sound without using strings or woodwinds, just some kind of 'pad'. The same applies to hits and rhythmic devices.
Anyway, the main instruments I use are Atmosphere, Stylus, A.I.R, Tsaiko, K2 & 3 libraries, K2 Experience & True Strike 1 & 2.
Horror movies are almost my favorite to watch and i watched The Entity, Let The Right One In, Cemetery Man, Dawn of The Dead, Pet Semetary and In The Mouth of Madness. I prefer to watch all these movies at my home. These all movies are very famous in Hollywood.