I've heard good things about Deadgirl, I watched about half of it but had to go do other things. It's not so much horror, but more snuff zombie kinda deal, I can see puddi getting his rocks off to it.
Not horror, but something with a great plot twist would be Fight Club, but who hasn't seen it? Ending is epic and worth more than a few watches.
There really isn't a whole lot of good horror movies though, but my recommendations are:
Last House On The Left (both old and new)
Silent Hill (kinda creepy and does well to portray the game)
House Of Wax
House Of A Thousand Corpses (or anything by Rob Zombie really)
Cannibal Holocaust (kinda old but I liked it)
Haunting In Connecticut