I think you're thinking of Evil Dead, there was no tree-on-woman rape in Night of the Living Dead.
Just a few nobody's mentioned yet: May, Audition (for strong stomachs only!), The Hills Have Eyes (the original is much better than the new one), Return of the Living dead.
Mick stole my go-to answer, I really think 28 Days Later is probably the best horror movie of the decade, so far.