Grand Theft Auto: IV
"D, motherf*cker, D, as in Drive!"
-- Citizen in car [usually behind you - in traffic]
I like a few of the quotes from San Andreas when driving:
"Inbreeding makes you dumb, huh?"
"You hit me! I'm-a hit you back!"
"Now you can buy a new one!"
"Where did you steal your license?"
"Who let you out of the mental home?"
"No! I ascertained! Me, Quassi!"
Far Cry 2
Every single line of dialogue in Grim Fandango (so far at least)
Caleb from Blood and Blood 2 has some of the best lines:
"I'm gonna paint the town red..."
"They're all dead, they just don't know it yet!"
"But I like my hands bloody."
"And along came a spider and sat down beside her and said, "What's in the bowl... bitch?"
"When you get to hell, tell 'em I sent you, you'll get a group discount."
"I'll have a BLT, that's a lettuce, tomato, and blood sandwich. Hold the mayo. HA HA HA!"
"They're gonna need a bucket and a mop when I'm done with you!"
"I'm here to donate some blood. Somebody else's..."