Okay, so future grief-stricken widow is the one to beat.

Penny: So, you know, isn't there maybe some way you and Sheldon could compromise on this whole presentation thing?
Leonard: No. Scientists do not compromise. Our minds are trained to synthesize facts and come to inarguable conclusions. Not to mention Sheldon is bat-crap crazy

Leonard: Two can play this game.
Penny: Get up.

Penny: Yes, I will go out with you.
Leonard: Really?
Penny: Yeah. Why not? I mean, what do I have to lose?
Leonard: Yeah. That's the spirit

Penny: Leonard isn't the kind of guy I usually go out with.
Sheldon: Leonard isn't the kind of guy anyone usually goes out with

Leonard: You know what? That was pretty crappy of you. All I wanted to do was to give you a great night and it was like you went out of your way to destroy it.
Penny: Yeah, I know. I'm a total bitch.
Leonard: I'm not saying that.
Penny: Well, I am.
Leonard: Oh, fine you win. You're a bitch.

Penny: Maybe we should talk first.
Leonard: Okay, but before you say anything, have you ever heard of Schrödinger's cat?
Penny: Actually, I've heard far too much about Schrödinger's cat.
Leonard: Good.
[Leonard kisses Penny]
Penny: Alright, the cat's alive. Let's go to dinner

Sheldon: Leonard made it very clear, he doesn't want a party.
Wolowitz: Did someone say party?
Penny: He just doesn't know he wants one because he never had one.
Wolowitz: I suppose that's possible, but for the record I've never had a threesome and yet I still know I want one.
Penny: Howard here's a difference: the possibility exists that Leonard could have a birthday party before hell freezes over.
Wolowitz: Fine, if I do have a threesome you can't be part of it... I'm just kidding. Yes, you can. Can you bring a friend?

Leonard: We think we can help you with your stage fright.
Sheldon: Oh, I doubt that. I haven't figured out a way, and I'm much smarter than all of you.
Penny: Yes, buy you're not smaller than all of us put together.
Sheldon: I'm sorry, that is what I meant.

Leonard: How did you know my birthday's Saturday?
Penny: I did your horoscope, remember? I was going to do everybody's until Sheldon went on one of his typical psychotic rants.
Sheldon: For the record, that psychotic rant was a concise summation of the research of Bertram Forer, who, in 1948, proved conclusively through meticulously designed experiments that astrology is nothing but pseudoscientific hokum.
Penny: Blah, blah, a typical Taurus

Penny: Is that why they're called Fig Newtons?
Sheldon: No. Fig Newtons are named after a small town in Massachusetts. No, don't write that down!

Howard: I got pretty exciting NASA news today. Next week I fly to Houston for orientation and zero-gravity elimination drills.
Penny: What does that mean?
Bernadette: He's gonna to learn to poop in space.
Howard: Open the pod bay doors, HAL.
Raj: Maybe your nickname should be "Brown Dynamite."

TBBT Quotes

Oh, Bernadette, please play my clarinet.

Raj's poem

Sheldon: I'll have a diet Coke.
Penny: Can you please order a cocktail? I need to practice mixing drinks.
Sheldon: Fine... I'll have a virgin Cuba Libre.
Penny: That's... rum and Coke without the rum.
Sheldon: Yes, and would you make it diet?