Examples of why I adore Professor McGonagall:
Professor McGonagall to Umbridge: "I wonder how you expect to gain an idea of my usual teaching methods if you continue to interrupt me? You see, I do not generally permit people to talk when I am talking."
Professor McGonagall: "I doubt it will make much difference, unless a mad axe-man is waiting outside the doors to slaughter the first into the entrance hall."
"It’s not a case of what you’ll permit, Minerva McGonagall. Your time’s over. It’s us what’s in charge here now, and you’ll back me up or you’ll pay the price."
And he spat in her face.
Harry pulled the Cloak off himself, raised his wand, and said, "You shouldn’t have done that."
As Amycus spun around, Harry shouted, "Crucio!"
The Death Eater was lifted off his feet. He writhed through the air like a drowning man, thrashing and howling in pain, and then, with a crunch and a shattering of glass, he smashed into the front of a bookcase and crumpled, insensible, to the floor.
"I see what Bellatrix meant," said Harry, the blood thundering through his brain, "you need to really mean it."
"Potter!" whispered Professor McGonagall, clutching her heart. "Potter — you’re here! What—? How?" She struggled to pull herself together. "Potter, that was foolish!"
"He spat at you," said Harry.
Lee Jordan was finding it difficult not to take sides.
"So-after that obvious and disgusting bit of cheating-"
"Jordan!" growled Professor McGonagall.
"I mean, after that open and revolting foul-"
"Jordan, I’m warning you-"
"All right, all right. Flint nearly kills the Gryffindor Seeker, which could happen to anyone, I’m sure…"