Your favorite gangster film that rarely gets talked about in gangster movie discussions

I’m watching Killing Them Softly (2012) right now, and I’m really enjoying the dialogue and grittiness. I definitely can see why it isn’t super popular and more of cult film vibe. It’s not flashy, it’s very dark even for a gangster film, and it’s unnecessarily confusing for a relatively straightforward movie. What’s your pick?

Edit: I see a lot of what I would call gangster adjacent films like Heat being suggested. While Heat has gangster elements and De Niro’s character deals directly with Nate the fence played spectacularly by Jon Voight, it is not a gangster film. You’re more than welcome to disagree, but it focuses more on the cops and thieves lives and relationships than mob activity. An example of a gangster movie: Sexy Beast, Eastern Promises, Casino etc.