S3, Mystery Spot

Sam: Man, I had a weird dream.
Dean: Yeah? Clowns or midgets?

Dean: Was it cool? Like in the movies?
Sam: You peed yourself, Dean.
Dean: Well of course I peed myself. Man gets hit by a car you think he has control of his bladder? Come on!

Brochure: "Where the laws of physics...have no meaning."

Sam: Like 'Dingos Ate My Baby' crazy?

Trickster: You can't save your brother. No good comes out of it--just pain, and blood.

Trickster: You're Travis Bickel in a skirt.

Sam: Just--bring him back. Please.

2x9

Sam: Dean, did you pay attention to History class at all?

Dean: Yeah, shot heard round the world, how a bill becomes a law...

Sam: That's not school. That's School House Rock.

2x7

Dean: My name is Dean Winchester. I'm an Aquarius, I enjoy sunsets, long walks on the beach and frisky women. And I did not kill anyone. But I know who did. Or rather "what" did. Of course, it can't be for sure, because our investigation was interrupted. But our work in theory, is that were looking for some kind of Vengeful Spirit.

2x6

Dean: L.A. A young girl got kidnapped by an evil cult.

Sam: Yeah, and does this girl have a name?

Dean: Katie Holmes

Sam: That's funny... and for you, so bitchy.

2x5

Dean: Demons. Spirits. Things your worst nightmares wouldn't even touch. Sam here is my brother.

Sam: Dean, shut up!

Dean: I'm trying. He's psychic, kinda like you. Well, not really like you, but, see, he thinks you're a murderer, and he's afraid he's going to become one himself, because you're all part of something that's terrible, and I hope the hell he's wrong, but I'm starting to get a little bit scared that he might be right.

2x4

Dean: Sam, you and dad, you’re the most important people in my life. And now... I never should have come back Sam, it wasn't natural, and now look whats come of it. I was dead and I should've stayed dead. You wanted to know I was feeling, well thats it. So tell me, what could you possibly say to make that alright?

I've been trying to stick to S3, but I have to pull this one from The Benders, S1

Dean: You hurt my brother and I swear to God I will kill you, you hear me? I will kill you all!

And a bookender from Devil's Trap,

Meg: He begged for his life with tears in his eyes. That's when I slit his throat.
Dean Winchester: For your sake, I hope you're lying. 'Cause if it's true, I swear to God, I will march into hell myself and I will slaughter each and every one of you evil sons of bitches, so help me God.

1x18

Sam: I wish I could have that kind of innocence.

Dean: If it means anything, sometimes I wish you could, too.

1x14

Dean: As long as I'm around, nothing bad is gonna happen to you. Now then, I know what we need to do about your premonitions. I know where we have to go.

Sam: Where?

Dean: Vegas.

One more from Devil's Trap

Dean: ...'cause I got a Yorkie upstairs, he pees when he's nervous.

(thought of this quote when I first heard about Icarus)