(Written for the newts500 Gryffindor challenge.)
The Hat smelled of dust and other peoples' heads, and was entirely too large for the ginger-haired boy. It settled over his eyes, tickling the bridge of his long nose, and he held his breath to keep from sneezing.
"Aha," murmured a small voice in his ear. He couldn't repress an excited shiver. The four Houses of Hogwarts were the touchstones of wizarding Britain; the next few moments would help define his life.
"..I know exactly where to put you," said the Hat.
It had made up its mind? That wasn't supposed to happen--
"Wait!" thought the boy frantically. "Don't you have to ask me questions?"
"Why should I? You see--" and the Hat chuckled -- "I've already studied your mind back to front. I know you better than you know yourself."
For the first time in his life, Albus Dumbledore felt chilled to the bone.
"Prime, pureblooded wizarding stock," gloated the Hat. "Learned strategy at your father's knee, seeing the Houses as a system of advantages and drawbacks, started forming alliances on the train -- you're secretive, complicated, separating emotions from thoughts..."
"Put me in Gryffindor."
"But that's quite the wrong place."
"Put me in Gryffindor," Albus demanded.
"Excellent, excellent! In a few years you might be really intimidating." The Hat sighed. "No, lad, it's quite settled. There's only one House for you."
Albus waited a moment. Then he said slowly, "But it's not settled. You're still listening. You want to convince me."
"Subtlety," approved the Hat. "Another characteristic trait--"
"It's not settled," Albus insisted. "Don't I get a say?"
"Why should you, when it's obvious--"
"It would be too easy."
Silence. He was getting somewhere, he could feel it.
"People," said Albus, struggling to fit the words together, "people change their minds. There's more to strategy than ends and means. You can call me anything you want, but I only deserve it if I listen."
"I'd be more effective as a Gryffindor."
"Isn't it... courageous... to take the hard option if it'll make things better?"
The Hat was silent. Finally it said:
"Do you have any idea what Salazar Slytherin would have thought of that little piece of reasoning?"
The boy had run out of words. He waited, trembling.
"Well done," whispered the Hat. Then, deafeningly, it shouted, "GRYFFINDOR!"
Worried hands snatched the Hat off his head. Teachers fluttered round him, and voices came from all sides: "Five whole minutes?" "This must be a record--" "Does that mean he's a Squib?" "I thought the Hat had died or something--" "Who is he?" "What's wrong with him?"
"I'm okay," he protested, aware that the entire Great Hall was staring avidly. "No, the Hat was fine, I guess it liked me, we just talked..."
"Let him alone," ordered the Headmistress, a plump former Hufflepuff. "Poor lad, what an ordeal, I'm sure he doesn't want any more attention this evening... You may go to your table, Mr Dumbledore."
Students surrounded him. He stepped off the dais and walked into history.