The Devil Rides Out (1968)
As the introduction to this film on TCM explains, part of the reason it may not have been the big hit is because it had the unfortunate timing of being released after Roman Polanski's "Rosemary's Baby". Both films deal with the circumference of fear when a young couple are slowly initiated into a satanic cult, What "The Devil Rides Out" has going for it (besides being a tremendous Hammer production) is its sincere attempt to unnerve AND entertain. Christopher Lee is the rare good guy fighting the powers of black magic and while it does contain some of the inherent kookiness of late 60's Hammer films, it more often than not hits its mark with simple scares and imaginary creatures.
Family Portraits (1993)
Essentially three short films (Cutting Moments, Home and Prologue) compiled into one bleak trilogy, Douglas Buck's ultra low budget efforts aren't "scary" so to speak, but they're disturbing at a basic level. Full of silent, seething rage between its characters and long stares into space, when the violence does occur, it's all the more shocking for how Buck frames and introduces it.... "Cutting Moments" especially. These are the types of stories where acts of violence play out, almost mutely, behind closed doors and when the acts are sprung into the world, the neighbor will say "I never saw it coming. They were such nice people". Buck's career is relatively short, but his work is well worth searching out.
The Bloodstained Shadow (1978)
Antonio Bido's lesser known giallo shoehorns so much plot into its first half, it threatens to implode on itself. Retarded children locked in attics.... a seance.... the ubiquitous black-gloved killer and a painting that may contain the key to the whole thing. It's needlessly convoluted which lessens its impact once the mystery winds to its conclusion. It is a giallo, after all and deserves a Halloween watch.