For the classics I'd go with:
Witchfinder General
The Texas Chainsaw Massacre
Deep Red
Dawn of the Dead
The Evil Dead
Zombie Flesh Eaters
For modern-day horror:
Piranha 3D
Like Darth, most of my friends wouldn't give classic horrors the time of day (too boring, not gory enough & old-fashioned).So, I usually end up watching them on my own.