Not sure if these thoughts are what you're after but there are older films that 'pushed the envelope.' John Carpenter's The Thing instantly springs to mind. I first saw it in the mid 80's and it really shocked me. I'd never seen anything like it before. btw I had similar feelings when I first saw uncensored dvds of Lucio Fulci's Zombie, City of the Living Dead and The Beyond.
Saw and Hostel I find quite tame by comparison.