I won't watch the original version of The Texas Chainsaw Massacre. The remakes are just blatant gore-fests. The original really gives a sense of this family being completely batshit crazy. For me it's a hell of a lot more disturbing than the remakes.
I recently watched a movie called 'Martyrs'. It's a French Movie, so if subtitles aren't your thing, you'd be best off not watching it. Pretty gory, and it has been labeled as 'torture porn', which would put it in the same category as films like 'Hostel'. I personally don't think it is torture porn, mainly because there's a story and a purpose to what is going on. Hostel can't boast the same.
One of my favourite horrors is 'WAZ'. It's actually W,Delta,Z, but the Delta part is a triangle, and hence 'WAZ'. Anyway, it's another one that got placed under the torture porn banner, and it's nothing like, for the same reason that 'Martyrs' isn't. Funny as it may seem, it always makes me cry at the end. It also has Stellan Skarsgård in one of the lead roles, a fine actor from Sweden.
I also like J horror (the J stands for Japan) though they're made by various Asian countries. 'Freezer', 'Audition', 'One Missed Call', 'Shutter' , 'The Eye' 'Dark Water' and the original Ring Trilogy (with 'Ring 0' being my favourite) are all great horrors. Some of them have been given the American remake treatment, and invariably the American versions are absolute gash IMHO. Again, if you're not into subtitles, don't watch them.
If we're talking classics, you've got to include 'An American Werewolf in London'. Even though we have computer graphics these days, I have never seen the transformation from man to Werewolf look as believable as it does in that movie. Small wonder that Rick Baker won an Oscar for Best Makeup because of it. The film has an awesome soundtrack too.
Last but not least, John Carpenter's 'The Thing'. I still find it's not always a good idea for me to watch this movie with the lights off, and it's probably one of Carpenter's finest films.