The Dark Knight // Christopher Nolan (2008)

The Joker: Well, you look nervous. Is it the scars? You want to know how I got ‘em?
[He grabs Rachel’s head and positions the knife by her mouth]
The Joker: Come here. Hey! Look at me. So I had a wife, beautiful, like you, who tells me I worry too much. Who tells me I ought to smile more. Who gambles and gets in deep with the sharks… Look at me! One day, they carve her face. And we have no money for surgeries. She can’t take it. I just want to see her smile again, hm? I just want her to know that I don’t care about the scars. So… I stick a razor in my mouth and do this…
[the Joker mimics slicing his mouth open with his tongue]
The Joker: …to myself. And you know what? She can’t stand the sight of me! She leaves. Now I see the funny side. Now I’m always smiling!