[i]Quotes are from link

"Lost: Live Together, Die Alone (#2.23)" (2006)
Desmond: [after Locke smashes the computer] You killed us... you killed us all

Desmond: I love you, Penny.

Desmond: Three days before you came down here, before we met, I heard a banging on the hatch doors, shouting. But it was you John, wasn't it? You say there isn't any purpose, there's no such thing as fate. But you saved my life, brother, so that I could save yours.
Locke: No, no, no, no! None of this is real! Nothing is gonna happen, we're gonna be OK!
Desmond: I've gotta go. And you've gotta get as far away from here as possible.
Locke: Go where? Stop!
Desmond: I'm gonna blow the dam, John! I'm sorry for whatever happened that made you stop believing. But it's all real. And now I've gotta go and make it all go away.
Locke: Wait! Desmond!
Desmond: I'll see ya in another life, brother!

[Charlie is trying to wake up Eko because he's unconscious. Charlie sees Desmond]
Charlie Pace: Hey! Can I get some help?
[Desmond looks for something in the library and ignores him]
Desmond: I'm trying, brother!

Desmond: [after looking at the printout Locke and Eko found] I think I crashed your plane.

Desmond: Ignorance is bliss.

"Lost: The Constant (#4.5)" (2008)
Desmond Hume: Who are you? How do you know my name?

Penny Widmore: Hello?
Desmond Hume: Penny?
Penny Widmore: Desmond?
Desmond Hume: Penny... Penny, answer. Answer, Penny
Penny Widmore: Des, where are you?
Desmond Hume: I'm... I'm on a boat. Um... I've been on an island, and - - Oh, my god, Penny. Is that really you?
Penny Widmore: Yeah! Yes, it's me!
Desmond Hume: You believe me? You still care about me?
Penny Widmore: Des, I've been looking for you for the past three years. I know about the island. I've been researching and then when I spoke to your friend Charlie, that's when I knew you were still alive. That's when I knew I wasn't crazy. Des, are you still there?
Desmond Hume: Yes, yes, I'm here! I'm still here, can you hear me?
Penny Widmore: Yeah, yeah, that's better.
Desmond Hume: I love you, Penny. I've always loved you. I'm so sorry. I love you!
Penny Widmore: I love you too.
Desmond Hume: I don't know where I am, but…
Penny Widmore: I'll find you, Des.
Desmond Hume: I promise
Penny Widmore: - no matter what...
Desmond Hume: I'll come back to you.
Penny Widmore: I won't give up.
Desmond Hume, Penny Widmore: I promise. I love you.

Desmond Hume: I won't call... for eight years. December 24, 2004. Christmas Eve. I promise. Please, Pen.
Penny Widmore: If I give you the number, will you leave?
Desmond Hume: Aye.

Daniel Faraday: Who are you calling?
Desmond Hume: I'm calling my bloody constant.

Desmond Hume: Set your device to... 2.342 and make sure it oscillates at 11.
Daniel Faraday: OK, now, you... You're gonna tell me who told you those numbers.
Desmond Hume: You did.
Daniel Faraday: Wait a second. This is ridiculous.
Desmond Hume: I know about Eloise.

"Lost: Man of Science, Man of Faith (#2.1)" (2005)
Desmond: Are you him?

Desmond: So we saved the world together for a while, and that was lovely.

Desmond: Now type in exactly what I say... 4 8 15 16 23 42. Now press execute.
Locke: What's going to happen?
Desmond: Just push it!

Desmond: See you in another life then, eh brother?

[Jack's explaining his "excuse" for his tour de stade after injuring his ankle]
Jack: Just trying to work a few things out.
Desmond: Ah, a girl, right?
Jack: A patient.
Desmond: Ah, but a girl patient. What's her name?
Jack: Her name's Sarah.
Desmond: What'd you do to her, then?
Jack: Do to her?
Desmond: You must have done something worthy of this self-flagellation.
Jack: I told her... I made her a promise I couldn't keep... I told her I'd fix her and I couldn't. I failed.
Desmond: Right. Just one thing - what if you did fix her?
Jack: I didn't.
Desmond: But what if you did?
Jack: You don't know what you're talking about, man.
Desmond: I don't? Why not?
Jack: Because with her situation that would be a miracle, "brother."
Desmond: Oh, and you don't believe in miracles?
[Jack laughs and shakes his head]
Desmond: Right. Well then, I'm going to give you some advice anyway. You have to lift it up.
Jack: Lift it up?
Desmond: Your ankle. You have to keep it elevated. It's been nice chatting.
Jack: Jack.
Desmond: Jack, I'm Desmond. Good luck, brother. See you in another life, yeah?

"Lost: Tricia Tanaka Is Dead (#3.10)" (2007)
Sawyer: Hey, Oliver Twist! Where the hell's my stuff?
Charlie: What stuff?
Sawyer: You know good damn well what stuff. I had books, food, porno, a bottle of scotch.
Desmond: Apologies for the scotch, mate.
Sawyer: You drank it?
Desmond: Well, to be fair, there were three of us.
Charlie: Yeah.
Sawyer: [to Desmond] You, the munchkin, and who else?

Desmond: You're gonna die Charlie, and there's nothin' I can do to stop it.

"Lost: Greatest Hits (#3.21)" (2007)
Charlie Pace: I want you to give this to Claire for me...
Desmond Hume: What is it?
Charlie Pace: It’s the five best moments of my... sorry excuse for a life...”My greatest hits"... You know... memories... they’re all I’ve got...

Desmond Hume: You don't have to do this, Charlie.
Charlie Pace: What?
Desmond Hume: I'll go.
Charlie Pace: No, your flashes...
Desmond Hume: Maybe I keep seeing you die because I'm supposed to take your place.
Charlie Pace: What about your girl, Penny?
Desmond Hume: What about your girl? Besides, I might be luckier than you.
[gives him back his "Greatest Hits" list]
Desmond Hume: Keep your memories to yourself. I'll take it from here.
Charlie Pace: I don't know what to say.
Desmond Hume: Well, you can tell me where the, uh, weight belt is...
[Charlie knocks Desmond out with an oar when he turns around]
Charlie Pace: You and I both know... you're not supposed to take my place, brother.

"Lost: Flashes Before Your Eyes (#3.8)" (2007)
Charlie: So, you're telling me you saw a flash of Claire drowning this morning, so you knew how to save her?
Desmond: I wasn't saving Claire, Charlie... I was saving you. This morning, you dove in after Claire. You tried to save her but you drowned.
Charlie: What do you mean? I didn't drown.
Desmond: When I saw the lightning hit the roof, you were electrocuted. And when Claire was in the water, you drowned trying to save her. I dove in myself so you never went in. I tried, brother. I've tried twice to save you, but the universe has a way of course-correcting, and I can't stop it forever. I'm sorry - I'm sorry because, no matter what I try to do... you're gonna die, Charlie.

Desmond: How do I know you?
Charlie: I don't, um...
Desmond: Where do I know you from?
Charlie: I don't know, but I'll remember if I could get some help.
Desmond: [Sees a flashback to the island] You're Charlie!
Charlie: Yeah, name's on the sign.
Desmond: It, it was in the hatch! I remember seeing you! There was a computer, there was a button... we were on an island!
Charlie: We are on an island, mate. This is England.
Desmond: No, it was real! I remember.
Charlie: Hey, all right.
[to the crowd]
Charlie: This is why we don't do drugs.

"Lost: Because You Left (#5.1)" (2009)
Daniel Faraday: The rules, rules don't apply to you. You're special. You're uniquely and miraculously special.
Desmond Hume: What are you talking about?

"Lost: Orientation (#2.3)" (2005)
Jack: Are you in contact with the people that made it... the film? Are you in contact with anyone?
Desmond: [trying to fix his computer] Do you think I'd be here if I was?
Jack: How is it that you didn't know about the crash? About us?
Desmond: I push this button every 108 minutes. I don't get out much.
Jack: So, these replacements?
Desmond: Kelvin died waiting for his replacements.
Jack: So you don't get out, you don't see anyone. Where does your food come from? You really think this is happening.
Desmond: Why wouldn't it be?
Jack: It says quarantine on the inside of the hatch to keep you down here. To keep you scared. But you know what? We've been up there for over 40 days and no one's gotten sick. You think that this is the only part of it that's true? Do you ever think that maybe they put you down here to push a button every 100 minutes just to see if you would? That all of this, the computer, the button, it's just a mind game? An experiment?
Desmond: Every... single... day. And for all our sakes, I hope it's not real. But the film says this is an electromagnetic station. And I don't know about you, brother, but every time I walk past that concrete wall out there, my fillings hurt.

"Lost: Further Instructions (#3.3)" (2006)
Desmond Hume: Yeah, right, Radzinsky. You never want to tell me what bloody hell happened to him.
Mike: You see that brown stain there? That's Radzinsky. He put a shotgun in his mouth while I was asleep. And you know what the bitch of it was? I only had a hundred and eight minutes to bury him. Poor bastard.

"Lost: Ji Yeon (#4.7)" (2008)
Desmond Hume: She just jumped!
Captain Gault: It's over. She's gone. Everybody get back to your posts. That was an order.