I've got so many but I love... XD:

Harry: "And request that he keep his abnormally large nose out of other people's business."
Severus: "Why, you insolent, little --"

Hermione: "Now, if you two don't mind, I'm going to bed before either of you come up with another clever idea to get us killed. Or worse, expelled."
Ron: "She needs to sort out her priorities."

Sirius: "The tail I could live with; but the fleas - they're murder."

Harry: "Don't forget the pincers... -click click click-"
Hagrid: -Gives him funny look-

Harry: "Now if you don't mind, I will be going now."
Slughorn:"Harry!"
Harry: "Sir?"

Harry: "Okay fine, you're in love with her, have you actually met her?"
Ron: "No.. could you introduce me? -grin-"