I got a lot of favorites can't think of them, my most recent favorite was in Pineapple Express:
Dale: So did anyone call you and ask about Pineapple Express?
Red: Uh uh...
Saul: Uh uh.
Dale: Uh uh?
Red: Uh uh...
Dale: Wait, was it "uh uh" or "uh huh"?
Red: It's uh uh
The way Red says his last line kills me, he says it like a snappy girl. And the fight scene following is hilarious.