You know there's something wrong with the series when the top 3 of this list contains the main character of your 3 latest installments.
That being said, i didn't find Tidus as annoying as some. He ends up as a decent guy.
Vaan however was completely lost to me and got my vote.
Same as Lightning, forgettable in XIII, she may redeem herself in XIII-III though. (although part of the problem was the game itself)