It wasn't a conversation, but Shepard getting so drunk he/she passed out on the floor of the men's bathroom was pretty goddamn hilarious. Especially with the turian in there going, "Wtf?"
This recruits, is a twenty kilo ferrous slug. Feel the weight. Every five seconds, the main gun of an Everest-class dreadnought one to 1.3 percent of light speed. It impacts with the force of a 38 kiloton bomb. That is three times the yield of the city buster dropped on Hiroshima back on Earth. That means Sir Isaac Newton is the deadliest son of a bitch in space! Now, Serviceman Burnside! What is Newton's First Law!
classic.
"This means that Issac Newton is the deadliest son of a **** in space!!"
Also, all the Garrus romance conversations, especially his attempts at seduction. "Your hair is...nice. And your waist is...very supportive.", And Mordin's advice on how to.... y'know.
Grunt when he discovers his hatred and purpose - that speech about the dead turien is awesome chilling. And then when he says he hates Turiens, and Sheprad warns him off Garrus.... it's gold!
Garrus and Tali on the Citadel, talking about old times.
"Tell me again about your immune system" "I have a shotgun." "Maybe we'll talk later."
"Put more stuff in the... the thing the stuff goes in."
It's hard to narrow the great conversations in this game down, really. There are far too many.
Shepard: Conrad, do you have any actual combat training? Conrad Verner : I'm saving the galaxy Shepard! I don't have time for training! Don't you get it?!
Shepard: I'm only gonna say this once, Conrad. *shoots in foot* this is NOT acceptable.
"If you need a problem shot, ask a turian. If you need a problem talked to death, ask an asari. If you need a new problem, ask a salarian. If you need a problem *solved*, ask a human".
That that one reminds me of my other favorites in the same dialog. Aria: explains her ONE rule. Sheperd: "I have similar rules" Aria: And on your ship that would matter, but here we entertain my prefrences.
So badass.
For me, the best thing about Aria's one-rule is not necessarily the dialogue, but everything else that goes with it. Carrie-Ann Moss delivers the line with style and flair. The direction of the camera shot, zoomed in as a close up on her mouth as she says it. The timing. It's an exceptional moment in ME2. Pure cinema.
But yes, I agree. Some of Shep's Renegade lines are very good.
"I'll relinquish one bullet. Where do you want it?"
"What, are you gonna kill us?" "If I have to. Do I have to?"
"Hostages only work when your enemy cares if they live"
etc etc ... Now if only BioWare had the $$ to hire Shane Black for the dialogue in ME3.....