A Clockwork Orange was fairly unique for it's time, but the opening sequence had actually been a homage, from what I've heard, to a movie by Andy Warhol. Though, again, that hardly keeps it from being unique. :P

And really, "A Clockwork Orange" is a movie not meant for a LOT of people, as it can, at times, be generally grueling to sit through.

And another movie I've always felt was fairly different, I will admit, was Ichi the Killer.