This is arguably the greatest horror film ever made. In a lot of ways, this 27-year-old classic shows its wear, but it still remains the template for how to do the scares right. Nominally about Good vs. Evil, as a pair of Catholic priests called in by a desperate mother struggle to save the soul of a little girl possessed by a demon, the film can be viewed as an allegory about Religion vs. Science, as the “witch doctors” only step in after the medical profession throws up its collective hands. Masterfully directed by William Friedkin.