...too many to choose from. I could make a huge post of my favorite conversations, but I'll just go with my favorite lines, as per the thread title.
From Origins (funny followed by serious):
Morrigan: If I feel the need to suck anything of yours, Alistair, you'll be the first to know.
Lelianna: Ah...then let's see what's in those trousers. I like to make informed decisions, after all.
Zevran: But it is a marvelous bossom...I have seen women half your age who have not held up half so well. Perhaps it is a magical bossom?
Shale: I am made of rock. That does not make me dense.
Morrigan: Faith. How quickly those who have no answers invoke that word.
Morrigan: Victory without cost has little worth.
Justice: Apathy is a weakness.
From Inquisition(I didn't play 2. Also, I probably have too many Solas lines, because I like him.):
Cole:I'm sorry, Cole, but with your gift, I fear that you might see the path I now must walk in solitude forever. This fate is mine alone. Indeed, I would not wish it on an enemy, much less someone that I once cared for.
Solas: The wise must sometimes give people what they need, not what they want.
Varric: But we went on living. he lost everyone, but he still got up every morning. He made a life, even if it was alone. That's the world. Everything you build, it tears down. Everything you've got, it takes--and it's gone forever. The only choices you get are to lie down and die or keep going. He kept going. That's as close to beating the world as anyone gets.