Slevin: How do you justify being a rabbi... and a gangster?
The Rabbi: I don't. I'm a bad man who doesn't waste time wondering what could've been when I am what could've been and what could not have been. I live on both sides of the fence. My grass is always green. Consider, Mr. Fisher... there are two men sitting here before you, and one of them you should be very afraid of. Where's my money?
Slevin: Someone's trying to kill you.
Yitzchok: Who?
Slevin: Me.
The Boss: I hired you to do a job. It wasn't supposed to look like a job. So you take out the Israelis, bomb the damn building and now the job that was not supposed to look like a job is beginning to look very much... like a job.
Lindsey: What happened to your nose?
Slevin Kelevra: I was using it to break some guy's fist.
The Boss: That's all there is to it.
Slevin: Is that all there is to it?
Mr. Goodkat: Yup... That's all there is to it.
Lindsey: Thanks for the sugar, sugar.
Lindsey: I was just thinking that if you're still alive when I get back from work tonight... maybe, I don't know, we could go out to dinner or something?
Lindsey: We are dealing with a bona fide case of mistaken identity here.
Slevin: Yeah.
Lindsey: Things like that aren't supposed to be real. It's like amnesia.
Lindsey: Not withstanding, here you are and Nick's nowhere to be found, so... I'd say you're fucked.
Slevin: Fucked.
Lindsey: Shouldn't you be a little more worried about all this?
Slevin: I have ataraxia.
Lindsey: Ataraxia?
Slevin: It's a condition characterized by freedom from worry or any other preoccupation, really.
Slevin: Ok, I'm under the impression that you're under the impression that I owe you 96,000 dollars.
The Boss: No, you owe Slim Hopkins 96,000 dollars. You owe Slim, Slim owes me... You owe me.
Slevin: I have ataraxia.
Lindsey: Ataraxia?
Slevin: It's a condition characterized by freedom from worry or any other pre-occupation really.
The Rabbi: If there's one thing I know, is when someone is lying. A man in my position, that's all he has to go on. To know a lie when he hears it. It's the difference between life and death. Your own. Someone else's. That being said, he wasn't lying.
Slevin: I'm not gay.
Brikowski: I'm a cop.
Slevin: Well, I'm not a robber if you catch my drift.
The Rabbi: You're unlucky and nothing more than a frame of reference for the lucky Mr. Fisher. You're unlucky, so that I may know that I am not. Unfortunately, the lucky never realised they are lucky until its too late. Take yourself for instance, yesterday you were better off than you are today but it took today for you to realise it. But, today has arrived and it's too late. You see?
Mugger: Give me your wallet.
Slevin: Am I being mugged?
Slevin: You're not as tall as I thought you'd be.
Lindsey: Well, I'm short for my height.
Slevin: That makes sense because I can usually tell how tall someone is by their knock. You have a deceptively tall knock. Congratulations.
Lindsey: So it's a good thing?
Slevin: I open the door expecting you to be up here, you're down here. That combined with a low centre of gravity - forget about it.
The Boss: Y-you? Nahh... You're dead. You're dead.
Slevin: This isn't the first time this has happened, you know.
Lindsey: You mean this isn't the first time a crime lord asked you to kill the gay son of a rival gangster to pay off a debt that belongs to a friend whose place you're staying in as a result of losing your job, your apartment, and finding your girlfriend in bed with another guy?
Slevin: No, this is the first time that happened, but Nick has been painting me into corners since we were kids.
Slevin: How do you get to two men that can't be gotten to? You get them to come to you.
Answer: I've considered 2 possibilities. One being the answer given about his cover, but I think he may have actually had it. When Goodcat is pointing a gun in his face as a child, he doesn't look scared in the least. The death of his parents "killed him" giving him the condition. Later proof is when he tells the Boss "You can only kill me once."