STS9 (Sound Tribe Sector Nine) - Check them out I saw them at Bonnaroo this year and they melted my face off.
Explosions in the Sky - As mentioned above! Great stuff.
Also check out Ratatat, a little simple at some times but it is so well put together. Two guys that center almost everything around guitar beats.
If you want to go a bit ambient I'm listening to Shpongle's "Nothing Lasts... But Nothing is Lost" Really good techno, not really instrumental but I'm sure you'd dig it if you are asking about instrumental bands on a horror forum! I will give it some more thoughts and see what I come up with.
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