Okay, I love Snape, so here are a few good ones:

"That is the second time you have spoken out of turn, Miss Granger," said Snape coolly. "Five more points from Gryffindor for being an insufferable know-it-all."

"Oh, very good....Yes, it is easy to see that nearly six years of magical education have not been wasted on you, Potter. 'Ghosts are transparent.'"

And a couple from the sexiest guy ever:

Professor Lupin: Now repeat after me - without wands please - repeat after me, Riddikulus.
Class: Riddikulus!
Professor Lupin: Very good. A little louder please, and very clearly. Rid-di-kulus.
Class: Riddikulus!
Draco: [under his breath] This class is ridiculous.

[after being "attacked" by Buckbeak the hippogriff]
Draco: You're going to regret this.
Hagrid: Class dismissed.
Draco: You and your bloody chicken.

I have dibs on draco. Anyone who says otherwise will wake up tomorrow morning in canada. Lol jkjkjk (rowling)

oh gosh so so many but i'm gonna go with Severues and one that always makes me chuckle

"Another ten points from Gryffindor. I would expect nothing more sophisticated from you, Ronald Weasley, the boy so solid he cannot Apparate half an inch across a room."