GamersGate's Halloween Sale is actually one of the tastiest we've seen yet. As a vintage horror fan, I'd recommend cheesy yet astonishingly intricate adventure Realms Of The Haunting all day long, but there are many more up-to-date titles here too.
Such as Outlast for £3.75, Dead Island GOTY for £3.74 and Amnesia: A Machine For Pigs for £3.50.
Beware a weird little trap, though, in that there are currently two Amnesia bundles on the storefront. One is called the Frictional Bundle, the other is called the Amnesia Bundle, but the former is 88p dearer than the latter. Either way, you're now forewarned, so definitely check out the splash page and see what takes your macabre fancy. Then be sure to thank jaystan @ HUKD!