I've heard the Dark Knight is really really good, and i do plan to see it, but haven't yet.
My vote goes for Boondock Saints. I don't watch a whole lot of movies, but I watch that one almost every other time. Great action and great storyline. And very entertaining even when there isn't any action currently going on. The only thing that I don't really care for in the movie is that Willem Dafoe plays a gay guy. I don't have anything against gays or anything like that, I just think that it's 100% unnecessary in this movie.