Zodiac (David Fincher, 2007) 
I've never been that big a fan of Fincher's work, finding the queasy opulence of films like Seven and Fight Club not to my taste. Here, he tones it down and plays his hand relatively straightforwardly about the notorious serial killer who terrorized the Bay Area in the late 60s/early 70s and vanished, never to be solved. This film on one hand contains the standard procedural drama, laying out the facts of the case which have been well covered over the years. What makes this film work and how Fincher differentiates it from banality is the thread of male obsession that runs through. Obsession and compulsion can be used to describe the killer himself, as the Zodiac claims in the film. But the obsession of knowing the truth is what really drives this film. The three other main characters, the boy scout cartoonist, the hardened, boozy reporter, and the earnest detective at some point become all consumed with the details of the case and are unable to let it go. The performances of the three, Jake Gyllenhaal, Mark Ruffalo, and Robert Downey Jr., perfectly embody the determination and obsession that come with wanting to know what happen. They perfectly stand in for the audience as everybody wants to know who the Zodiac was and why he did what he did. But Fincher also succeeds in not really answering anything. The film wants to tag Arthur Leigh Allen as the Zodiac but all the psychical evidence in the case cannot be linked to him. The film doesn't have any more answers by the end than when it started. The strength of the film is that it can still be effective even though the entire course of it was a search for answers and it turned up nothing.
Fincher as the director here is a near perfect match. Someone who is notoriously detail obsessive as he fits the overall theme of the film perfectly. No detail in matching the period of the early 70s is spared all the way down to the studio cards at the beginning of the film. I've found Fincher's style to be a little overbearing in the past, but with this film, it fits consistently with the theme of the film.