"Did you kill much when you were alive?"
"Very little."
"Never killed anybody."
"I have to confess... I never killed anybody."
"Not even a teensy bit of killing?"
" MAYBE I JUST WASN'T TRYING HARD ENOUGH. "

Grim Fandango, it was a small conversation between manuel and mercedes.

You are correct. Go, man, go!

"Sure, we'll lose it too. But so what? Who gives a shit - we don't need cover, right?"

Sounds like a whiny smartarse bitch so my first thought is Baird from Gears Of War...

It's an annoying smart ass bitch from a different game...

Haven't responded since my INternet keeps crashing...I think it is the noscript add on. Anyways, I meant Postal 2...when the guy urinates. but go ahead. =)

Oh, I see.
Yep, I haven't ever played Postal or Postal 2 (and don't plan to do so, either- just not my cup of tea), but I'm quite sure the trainer in MM6 says this as well.
Anyway, the game went on.

Farcry 2. I think.

Right you are. Your turn.

"During this mission call me Major Tom."

This is a really nice thread.
MGS3, perhaps?
If I have guessetd it correctly, let me propose another one:
"More twinklies!!! More twinklies!!"

Is this from a shooter game?

The major tom quote was indeed from MGS3 so Villodre's quote is the current one.
However since I know its from the end of Sam & Max Hit The Road, I guess its my go.
"Let me rephrase the question: where the fuck is my bike and why haven't you fucking gotten it back, friend-brother?"