"Well, technically... It's a thingy." - Harold from Fallout 2 explaining technicalities of Hydroelectric magnetosphere regulator.
"You cut with the dull edge of the knife, don't you?" - Harold again
"I cannot be caged. I cannot be controlled. Undersand this as you die, ever pathetic ever fools." - Jon Irenicus unleashing his power on some fools who thought they captured him in Baldur's Gate 2
"Ok, I've just about had my FILL of riddle asking, quest assigning, insult throwing, pun hurling, hostage taking, iron mongering, smart arsed fools, freaks, and felons that continually test my will, mettle, strength, intelligence, and most of all, patience! If you've got a straight answer ANYWHERE in that bent little head of yours, I want to hear it pretty damn quick or I'm going to take a large blunt object roughly the size of Elminster AND his hat, and stuff it lengthwise into a crevice of your being so seldom seen that even the denizens of the nine hells themselves wouldn't touch it with a twenty-foot rusty halberd! Have I MADE myself perfectly CLEAR?!" - player character to some hermit speaking gibberish in Baldur's Gate
"Fool me once, shame on you; fool me twice, watch it! I'm huge!" - Minsc obviously
"Boo: *squeak*
Minsc: Boo says "WHAT?"" - Minsc and Boo
"(running away): Tiax will rule... From a distance." - Tiax, Baldur's Gate. Really, all his lines are hilarious
"We're all doomed.
Life is so hollow.
Oh, what is the point?
Our quest is vain.
Let us save our effort and just lie down and die!
Onward, to futility!" - Xan, Baldur's Gate
"Lo Wang: "If I kill myself will it kill you too? Please say yes."
Hoji: "Yes."
Lo Wang: "You're lying aren't you?"
Hoji: "Yes." " - Shadow Warrior 2013
"I always bring a katana to a gun fight!" - Lo Wang again