I loved some of the dialogue in POA:
Ron: [sitting bolt upright in bed] Spiders... the spiders... they want me to tap-dance. And I don't want to tap-dance!
Harry: You tell those spiders, Ron.
Ron: Yeah, tell them... I'll tell them...
[falls straight back to sleep]
Professor Snape: That is the second time you have spoken out of turn, Miss Granger. Tell me, are you incapable of restraining yourself, or do you take pride in being an insufferable know-it-all?
Ron: He's got a point, you know.
Ron: She's gone mental, Hermione has. I mean, not that she wasn't always mental, but now it's out in the open for everyone to see!
Dumbledore: Professor Kettleburn, our Care of Magical Creatures teacher for many years, has decided to retire in order to spend more time with his remaining limbs.
Ron: Neville, you're supposed to stroke it!