I think it's amazing when a writer can sum up a character with one line of dialogue, one telling action, one perfect piece of description or internal thought.
In the new Bond movie, a bartender asks Bond whether he'd like his martini shaken or stirred. Bond turns to the bartender, a slightly annoyed expression on his face and says, "Do I look like a man who'd care?" (or something like that)
What I love about this line is that it not only defines his character, but it also defines the new direction the franchise has taken. Bond is no longer a fastidious invincible cartoon hero but a real rough tough man who bleeds (and makes others bleed more).
So, what perfect characterization lines do you love? In a book, a movie, your own work...
Depending on your perspective, I'd like to say either, "You're welcome," or "I'm sorry," for this uncharacteristically short post.