I'm thinking Reznor is an INFJ. (Oddly enough, in the Marilyn Manson thread the consensus seems to be that he's an INFJ, while I think Manson is INTP; whereas here a couple of people have suggested Reznor is an INTP and I think he's INFJ).
Trent Reznor is one of the most notorious control freaks in the music industry, second perhaps only to Prince. He IS Nine Inch Nails, and he will allow no one to take any credit or have any input into that band. Even Chris Vrenna, who stuck by him during the ramen noodle-subistence days when they were nobodies, was being paid a pittance for his work in NIN. To a man, the musicians who've toured with him describe Reznor as a taskmaster. Onstage, he was shockingly violent to his bandmates -- even Marilyn Manson, who could be vicious, wasn't as violent as Reznor. I've seen concert footage of Reznor attacking his bandmates, tripping them, dragging them by the hair, and one incident where he ran up behind guitarist Robin Finck and attempted to sodomize him with a microphone.
He can also be manipulative to get what he wants. Charlie Clouser and Jerome Dillon have both discussed how Reznor talked them into his employment with promises of producing records for them or incorporating them into special projects such as the stillborn Tapeworm, but none of those promises went anywhere. When Dillon had heart trouble, Reznor dumped him off at the hospital and found a touring replacement, then after Dillon recovered basically blew him off.
As has been noted, Reznor's music was very forward-thinking and N-ish. He's clearly introverted and doesn't seem to have many close associates left, aside from his wife and Atticus Ross and whoever he hires to hang out with them (Marilyn Manson once mocked him as 'Rent Friendster', alluding to Reznor's habit of hiring and firing 'friends'). He even met his wife Mariqueen on the internet (on Twitter, no less). Reznor is also known for starting and then dropping projects left and right -- Tapeworm, his would-be collaboration on Abraham Lincoln: Vampire Hunter, etc. This is a guy with a brilliant mind and no sense of direction or focus.