So; I was rereading the whole series recently and something almost insignificant just kinda popped out of the page at me.
First off, we all know Luffy's "X" scar that he now has on his chest post time-skip; and how he carries the "Will of D" and has the Conqueror's haki.
I just noticed that Coby has an extremely similar scar when he seems to use the Conqueror's haki as well at Marineford. It's on his forehead in the bottom frame. I haven't gone back through to see if Gol D. Roger had it as well anywhere that was noticeable; but is it possible that only those that are going to become leaders of their era will have this scar on their body somewhere? Who else has it that we know of?
(Not sure where images are generally posted from, I just took it from where I was reading it off of....)