I'm not quite sure what you are asking when you say "push the envelope". When I hear that term used in horror, I generally think of films like August Underground, Nekromantik, A Serbian Film, etc. It seems you are speaking more along the lines of mainstream films and with that in mind, are you meaning in terms of creativity or actually stepping over the usual boundaries related to onscreen violence and nudity? You mentioned Friday The 13th Part 2 a couple of times, and as far as that film goes, there are films today that are mainstream and have full frontal nudity, like Piranha 3D or the My Bloody Valentine remake. There have been quite a few that have come up with some creative kills too since the 80's, films like Wrong Turn, the Saw series, Final Destination, and so on.
As far as creativity in the films themselves, it's rare that anything out of Hollywood takes a chance and most often you need to look to other avenues like foreign imports and independent films.
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