Coach Oleander from Psychonauts.
I'll stick with my previous trend and keep mine easy:
"I think I'm in lust... er, love."

It sounds like Morte from Planescape Torment, maybe when meeting Fall From Grace.
I agreed with him

Yep, that's it.

Damn, now I have to think of another quote...
“Questions, questions... go ahead, I’m all horns.”

Neeksha from NeverWinter Nights 2 hey? Good character that, I saved her instead of beating her to death with the mob.

Yeah she's a favourite of mine, I like weirdos and you can't get much weirder than her

True that. :)
Mine: (And it's easy)
How appropriate. You fight like a cow.

You're joking right? Right?!?
Monkey Island 1 - Riposte to "You fight like a dairy farmer"
Not going to wait for confirmation this time or someone will take my turn because I'm are work or sleeping or something.
""Worms and maggots fed upon his festering skin, the scent of tainted blood seeped through the wounds upon which they feasted. Pity, such a waste-- good blood gone bad."
Karl

That's one of Kain's lines from Blood Omen: Legacy of Kain.
And now I get to go again... I'm starting to run out of ideas...
Okay, here's a tricky one. The same game contains variations of this line, said over and over again in multiple locations by the same red-headed girl... or someone who looks like her...
"Me? I'm working here part-time."

OK, though I don't know Prator's one, I'll dare and post a new one, as it's been 14 hurs since it was posted. (Yeah, it's the same one I posted earlier but then it turned out it wasn't my turn. I'm curious who will guess it, if anyone.)
If someone answers Prator's one and claims ownership of this turn, I'll just edit it out again and save it for later ;-).
"Everything changes, Steven, everything!"

Well, great. We've both managed to pick out quotes that apparently no one recognizes. I guess that means the next turn is up for grabs...

These are hard! Just to see what they were I google them and didn't get anything.

The Longest Journey?

Indeed.