Most likely historical figure to have been a time traveller

[Caliga]

Mother died when he was a kid. Estranged from uneducated father. First lover died. Two sons died young, including one while in the White House. Wife increasingly crazy since the beginning. Leadership always second-guessed and criticized until assassination right after having abolished slavery, won civil war, and saved the nation.

Bitchin' beard, though.

[Barrister]

What the hell, I'll give a straight answer.

Thomas Edison, time traveller.

[Sheilbh]

Frederick II's always seemed very out of his time.

[dps]

William S. Burroughs

[Phillip V]

Most widely-acknowledged time traveler is Jesus of Nazareth.

[Josquius]

Why Lincoln?

Freakishly tall, progressive, great at presidenting (it's a word now dammit), generally odd.
Sure, a lot is known about his earlier life which needs to be ignored but still, he is a strange chap.

[alfred russel]

John McCain appears to be from an earlier era, as though he came of age in the 1950s.

[lustindarkness]

Most widely-acknowledged time traveler is Jesus of Nazareth.

Or an alien.

[Razgovory]

Frederick II's always seemed very out of his time.

Hohenstaufen or Hohenzollern?

[merithyn]

Freakishly tall, progressive, great at presidenting (it's a word now dammit), generally odd.
Sure, a lot is known about his earlier life which needs to be ignored but still, he is a strange chap.

He was 6'4". That's not exactly "freakishly tall". George Washington was 6'2". And we've had a number of guys who were "great at presidenting" (damn, that was hard to type), and progressive.

[Valmy]

Frederick II's always seemed very out of his time.

Hohenstaufen or Hohenzollern?

RIght?  Could be either or both.

[garbon]

Mother died when he was a kid. Estranged from uneducated father. First lover died. Two sons died young, including one while in the White House. Wife increasingly crazy since the beginning. Leadership always second-guessed and criticized until assassination right after having abolished slavery, won civil war, and saved the nation.

Bitchin' beard, though.

Not really. Maybe bitchin' means gross in this context?

[jimmy olsen]

Shakespeare. Not only was he a time traveler, he was a Klingon time traveler!

[Queequeg]

Mohammed, or some of the early Caliphs.  Zoroaster. Zoroaster was preaching something radically different from the religion of his time, don't think there have been many people on his level.

[Viking]

Hitler and Stalin. They seem to be the two individuals in history who, from lowly beginnings of no consequence bestrode the world stage. Neither having the manual on how to succeed in running their country for the benefit of their people, they did both seem to have a manual on how to achieve power and once in power focusing on one single issue, hitler "getting" those he hated, stalin staying in power. They seem to both to have turned into annoyed gamers who suddenly realized that this is real life and they couldn't quit and have a sandwich at some point after the time when they themselves began to affect history rather than merely harnessing historical forces to their own ends. Neither seems to have been exceptionally competent, just insanely lucky with timing and strategy.

Yeah, that second to last sentence is a bit convoluted... but it is a sentence.

Perhaps it was that time in history rather than them being time travelers.

I agree, it was that moment in history when ANYBODY could have become a world striding conqueror if he just harnessed the correct revolution.