Originally posted by: Divinity
Ahhh so many different opinions.... hehe... I'm sitll gonna stick to my idea that Kakashi somehow copied Mangekyou Sharingan. First off, Sharingan is a bloodline limit and it can't be copied Yes, but Tsukoyomi is a jutsu and Kakashi probably copied it and gained access to the Mangekyou Sharingan.
Tsukiyomi and Amaterasu are both justu done with the MS through the eyes. There is nothing to copy, and Kakashi didn't copy it.
Originally posted by: Naruto_RNG
ofcourse kakashi is the 3rd user. what makes u think he isn't?
itachi killed every uchiha excluding his little brother. so the option of the 3rd unknown person is already done, which leaves u with kakashi.
There is always the possibility that Kakashi only just recently developed the MS, therefore he wouldn't be the 3rd user. It could be that the 3rd user was killed by Itachi (possibly Shisui), or that the first user ever has been dead for X-hundred years. We don't know.

But for the record, I'm starting to beleive it is Kakashi.