I'm not a purist at all so i don't mind if the movie is a contamination of different genres. Some of my favorites:
alien - ridley scott
the innocents - jack clayton
lost highway - david lynch
texas chainsaw massacre - tobe hooper
la casa delle finestre che ridono - pupi avati
deep red - dario argento
le locataire - roman polanski
coma - michael chrichton
the night of the living dead - george romero
the haunting - robert wise
shining - stanley kubrick
deliverance - john boorman
blood and Black Lace - mario bava
picnic at Hanging rock - peter weir
the thing - john carpenter
alien - ridley scott
the innocents - jack clayton
lost highway - david lynch
texas chainsaw massacre - tobe hooper
la casa delle finestre che ridono - pupi avati
deep red - dario argento
le locataire - roman polanski
coma - michael chrichton
the night of the living dead - george romero
the haunting - robert wise
shining - stanley kubrick
deliverance - john boorman
blood and Black Lace - mario bava
picnic at Hanging rock - peter weir
the thing - john carpenter