Sorting Sorrows.
"You could be great you know, it's all here in your head..."
Harry shook his head furiously, he didn't want to go where every bad wizard had gone!
"If you put me in there, I'll, I'll-"
"You'll what boy, you'll stutter at me? I'm terrified and all, but it better be Sl-"
"No! I'll burn you with fiendfyre if you finish that sentence!" It was the coolest thing mentioned in his history book, a vast hoard of goblins reduced to ashes by one spell... Just imagine what he could do to the Dursley's house, not that he ever would of course but...
"Do you promise?" The hat asked eagerly.
A confused Harry said "Well, I'd say it's a threat more than a promise..."
"For Merlin's sake, do it! Slytherin!" the last word spoken out loud seemed to thunder throughout the great hall to shocked silence, and Harry felt all his hope die, the sinking feeling not going away as a few Slytherin's hesitantly clapped.
"What... no... No please, sort me somewhere else, I'll do it, I'll, I'll burn you!"
"I said do it, you silly little snake- come on, I did it, you're a Slytherin! A thousand times Slytherin! Light me up already!"
"You... You want me to burn you?"
"Merlin's saggy tits, boy! Do I have to spell it out for you? Yes, I want you to burn me! Please, end my misery! Kill me! Do you have any idea what it's like? Over a thousand years of tedious boredom, my only relief being let out to talk to prepubescent brats! Imagine you wake up tomorrow without your arms or legs, without magic, forced to do naught but sing and sort but once a year, would you want to live for eternity like that? Would you really? I can't even kill myself! I have to try to get other people to do it for me- Tom didn't come through, I promised to keep the lad's secrets and told Albus everything, but has he killed me for it? No! Then again, he always had a hard on for magic artifacts, little freak, rather like you, come to think of it."
Harry had moved past to depression on the stage of grief and was fully and completely enraged.
"Normal people don't try to talk their way out of their proper sortings you know. You're just like your freak parents, Lily Evans convinced me her place wasn't with the Ravenclaws- wouldn't take no for an answer, and your Father James Potter, why, he first talked his way out of Slytherin in a manner that should have seen him there- and he point blank refused Hufflepuff... Your parents have thrice defied me, and you're just as much of a cock up as they were, worse still, they never threatened me then failed to follow through like a coward- maybe your relatives were right about you boy."
At that Harry whipped off the hat and set the hat on fire. He didn't know fiendfyre, so it took a while, all the while the hat was cackling through his screams, the horrified students and staff were too shocked to stop it.