Today's nominee is Sneakers.
I wonder why this movie made so small a splash. It has a fantastic cast full of big names, and lots of them. It was pretty well promoted back in its day. It's got plenty of action and a cutting-edge feel, even though the pacing is not frantic, it's measured and well-crafted, rather than just piled on and ratcheted up. Seems like a sure winner. But while it didn't bomb or anything, a lot of people are not even aware of it, or only faintly.
Looking at it solely as a heist movie, it's one of the best out there. It's also one of the best computer "hacker" movies, both in terms of an interesting plot, and in terms of realism (not to say it's perfect in that regard, but most of its inaccuracies are easily dismissed as simply time-condensing things that would be boring to watch more slowly, plus there's the MacGuffin, which isn't real, but is at least plausible). It's also a very good action movie. Plus it includes a fair amount of serious thoughts about the value of information, the balance between privacy and identity, and the impact an information society can have on politics, society, economics, and justice, for better and for worse. (Admittedly, some of that takes the form of slightly heavy-handed, though still story-appropriate, exposition.)
It's one of those movies that bears up very well to repeated watching. You don't start finding flaws; the closer you look, the more the plot fits together. You don't find it becoming hollow; you start appreciating more details, more foreshadowing, more subtlety in the acting and writing. It's a movie that sticks with you, not one that boils off the memory a minute after the credits roll.
It also has good laughs, and they're very natural laughs: they don't feel like people being artificially witty, but the kind of funny that you have with normal folks who happen to be funny. Okay, on second thought, "normal" isn't the right word. Some of these guys, especially Mother, are pretty weird. But when they're funny it's because of who they are, not because of who the writer was.