I've finally figured out who Darth Krayt is! There are three major possible people that it could be: Kyp Durron, Daye Azur-Jamin, or Someone else entirely.

1) Kyp Durron
I believe that Kyp could be Darth Krayt. Kyp has more in common with Krayt because of his personality and previous dealings.
Kyp was once possessed by the ancient Sith Lord Exar Kun.
He has had many times when he almost went to the dark side (many of which were during the Yuuzhan Vong war).
Kyp was alive during the Yuuzhan Vong war.
And reason #1: Kyp never agreed with the Jedi and almost started a schism within the order because of his aggressive tactics and use of force when needed.


2) Daye Azur-Jamin
The similarities between Daye and Darth Krayt are many.
A Yuuzhan Vong, (Vongerella) trained Daye and Darth Krayt has Yuuzhan Vong armor.
Daye is missing his right eye Darth Krayt seems to have something wrong with his right eye.
Daye and Darth Krayt were both alive during the Yuuzhan Vong war.
It hasen't yet been stated if Daye actually turned back to the light side of the force.

3) Someone else entirely
Vongerella's unknown master
Some random dark Jedi
Someone we've never even heard of
Maybe even Jorj Car'das

Also many people are under the misconception that Darth Krayt is Jacen Solo. This is completely wrong. Jacen didn't even begin teachings in the dark side until almost 10 years AFTER the Yuuzhan Vong war. Also the Darth Name contest says create your own name, which makes it impossible for Jacen to be Krayt. Another thing is that Jacen knew many things about the force and I doubt that he would use the Sith teachings as Krayt did in the preview for Legacy #5 instead of another force-using group. Plus in the tassel from Kessel says He will choose the fate of the weak, the opposite of Krayt wanted to rule the Galaxy.

Please feel free to point out any flaws in my theories.