The Exorcist (Directors Cut) (1973)
The lurky rainy sunday was concluded with this classic, in a new shape. A couple of new scenes that thickened the plot. Great phenomenon, but as to being the scariest movie ever, especially with the enormouse mood boost it got, what with the darkness, the candles, the rain, and the wind, I hardly concur.
Watch it, if the power of christ compels you!