While The Serpent and the Rainbow (1988) was a better acclaimed movie, I found The Believers (1987) to be one of the most frightening horror movies I’ve seen.

I had to walk home all by myself in -10 degree weather a half hour after I watched that movie. Scared the shit out of me.

EDIT

I also love The Skeleton Key (2005). Just something about voodoo and hoodoo movies that I find engaging.