Zodiac with Jake Glynnhal (sp), Robert Downey Jr. and Mark Ruffalo, 2000's.
I can remember seeing this in the theater ages ago and thinking it sucked. I obviously didn't know any better then because it's a very solid movie; evidently, my dumb ass thought it lacked action or something. I've watched it like 4 times in the past month now (not all the way through each time, but for long stretches) and it really is fantastic.