Bishop: All we know for sure is that he went to college with Amanda Kendall. His murder could be a coincidence.
Gibbs: McGee.
McGee: Rule 39, Bishop.
Bishop: Right. No such thing as a coincidence. I knew that one.

[after killing Salim] Let's go home.

Never assume. (Season 9, Episode 21)

Rule #8

I can't believe I called the POTUS a wise-ass

Tony

Gibbs: Banks? Banks? Talk to me Banks.
Banks: Hannah.
Gibbs: Hannah. Where you from Hannah? What hometown?
Banks: I tried to steer clear, Gibbs. Couldn't shake it.
Gibbs: Hey you are one hell of a pilot.

McGee: Boss do you think I made the right decision with my father?
Gibbs: To be the bigger man? Maybe it's time he learned from you, McGee.

Vance: Bad cop?
Gibbs: You've been playing good cop all this time?

There is no such thing as a small world. (Season 10, Episode 14)

Rule #39A

Gibbs: Cal, do something for me?
Cal: Sure. Anything. You want me to lock the back up?
Gibbs: I want you to take the store. Cheers. It's what dad would have wanted.
Cal: But I... I'm not... I mean, I don't even know how...
Gibbs: Just do the work.
Cal: I will.

Gibbs: What are you doing here?
Diane: I brought her. You two need to talk. And we all know that's not something you're interested in.
Gibbs: Got that right.
Diane: So I suggested that---
Gibbs: Ambush me at a crime scene so I can't get away?

If someone thinks they have the upper-hand, break it. (Season 8, Episode 24)

Rule #16

Gibbs: Whaddya got?
Tony: Crabs.
Borin: We have a problem.
Gibbs: Worse than DiNozzo's crabs?

NCIS Quotes

McGee: All right. Well you should probably know that Abby and I used to date?
Bishop: Ew. Like, each other?
McGee: Yeah.
Bishop: Wait - isn't that a violation of rule 12, never date a....
McGee: It was a long time ago. After we'd broken up, one night I went to her lab. Found a scribbled piece paper; a list. Potential boyfriends had to fulfill certain conditions by a pre-arranged date or else, goodbye.
Bishop: Such as.
McGee: Things started off relatively normal: opening the door for her, flowers, putting the seat down. Then around number 8, it gets uh...
Bishop: What?
McGee: Does she know you have these?
Bishop: Does she know you have these?
McGee: Yeah she wasn't happy when she found out.
Bishop: These are all very specific.
McGee: Yeah.
Bishop: These ideas apply to you?
McGee: No those rules weren't in place when we were together. At least I don't think so.
Bishop: What's with the two month cutoff? Abby's sabotaging herself. I've seen stuff like this before. We have to talk to her.

McGee: Rule number 70 - keep digging till you hit bottom.
Abby: McGee! There is no rule 70.
McGee: Well, I--
Abby: You just made up a rule. This McGibbs thing has really gone to your head. I don't even recognize you right now.