American Psycho (Dir. Mary Harron) 2000

Based upon the Bret Easton Ellis novel of the same name. AM is not what you would consider to be a genre specific Horror movie. In fact it is a black comedy, a satire that works on many levels.
The original novel was classed as unfilmable and misogynistic, a critique of 80's American wealth and corruption. So why not A) Get a Briton to play the American central character and B) have the film directed by a woman! This dynamic adds a little twist and taps into the novels disregard for genre conventions and PC appeasement.
Christain Bale is Patrick Bateman. Physically stunning, morally disgusting who is a city player by day and a murdering psychopath at night but these are almost afterthoughts as we are essentially ripping apart the American ideal of 'Money Is God' for the corrupt beast that it is.
Wonderful set pieces include the 'business card standoff' and the daily cleansing schedule of Bateman that are clearly huge satirical swipes at redundant consumerism. The horror aspect I hear you ask? It is rare and mainly off screen. This is the films masterstroke. Violence and psychotic behaviour is the least of Batemans appalling traits and the films twist ending reinforces this.
A special mention should go to the hilarious yet cringeworthy monologues that pertain to Batemans (very 80's) musical tastes and the verve and genuine love of all things cheesy have to be heard to be believed.
The music monologue and the crazy little dance sum this movie up perfectly: