No love for The Texas Chainsaw Massacre? The original is better, of course, but the remake is still a good choice; the difference is, do you want to be horrified and repulsed and say “oh Jesus” a lot (original) or do you want to jump a lot (remake)? Don’t bother with any of the sequels, though, they’re all pure crap.
Seconds for Audition, Dead Alive, Suspiria, The Descent, The Ring, The Exorcist, The Thing, the new Dawn of the Dead, Session 9, and others too numerous to mention in this thread.
If you’re wanting the ultimate in gore, if you think you can stomach it, seek ye the August Underground series. There are three: August Underground, August Underground: Mordum, and August Underground: Penance. Of the three, Mordum is probably the harshest; watching it is pretty much an endurance test. All three are “simulated snuff”, shot as though you’re watching the escapades of a serial killer and his buddies. The effects are very, very good.