Satan's Blood is a great film.
Don't Deliver Us from Evil is worth a mention. A creepy little exploitative French shocker about two young girls who make a pact with the devil. This is a personal favourite of mine.
The Devil's Nightmare is also quite entertaining and has Erika Blanc star as a demonic succubus. Filled with cheese and softcore sex and nudity, you can't really go wrong...
An Angel for Satan is another that is worth a watch. Barbara Steele stars in this fairly decent gothic mystery revolving around a statue and mysterious deaths in a village that has been attributed to witchcraft.
I'm also surprised Black Sunday hasn't been mentioned yet, but I guess that's a bit too obvious a choice
