Well quite obviously;

"I'm Gentleman Death in silk and lace, come to put out the candles." -Lestat

This one always makes me laugh;

Once Armand had dragged Daniel out of bed in New Orleans and shouted at him: "That telephone, I want you to dial Paris, I want to see if it can really talk to Paris."
"Goddamn it, do it yourself," Daniel roared. "You're five hundred years old and you can't use a telephone? Read the directions. What are you, an immortal idiot?"

I think Louis says this while in the Teatre des Vampires descusing God and the Devil with Armand.

And what constitutes evil, real evil... Because if God does not exist, then life... every second of it... Is all we have. - Louis

I love this quote. Lestat says this to Louis at the end of Queen of the Damned, when he's insisting that Lestat is a perfect devil. I think it sums up Lestat quite well.

Tell me how bad I am. It makes me feel so good! - Lestat

From interview with the vampire film.

Lestat: For you, Louis. You can pretend it's wine.

I also love;

Lestat: [dancing around with the corpse of Claudia's mother] There's still life in the old lady yet!

I love in Queen of the Damned when Gabrielle says something like, "How do I waste this bitch?" takling about Akasha. every time it makes me laugh.

^ ditto =D

"Ah, come now. I look like an angel, but I'm not. The old rules of nature encompass many creatures like me. We're beautiful like the diamond-backed snake, or the striped tiger, yet we're merciless killers."-Lestat

"I can't help being a gorgeous fiend, it's just the card I drew"-Lestat

"Sweet to think on it, that when we are last weary of all this world there is the rising sun." -Armand

I love when he says this!

"If I'm an angel paint me with black wings." -Armand

"Real evil, is the taking of a single human life. Whether a man would die tomorrow or the day after or eventually... it doesn't matter. Because if God does not exist, then life... every second of it... Is all we have." -Louis