When the swashbuckler's confirms a critical, she may use a free action to "mark" the opponent. She gains a +2 bonus on Diplomacy and Intimidate against that opponent and whoever else happens to watch the fight. since they are so impressed by the swashbuckler's skills and style.
It'd be a pretty cool ability and it that does not make him much stronger in combat. You could call it "The Mark of the Fox".
I know it's kinda of silly... I just want a way to leave big Z shaped scars on male opponents and cut the dresses of female opponents.
Other things that would be cool, but probably too strong... adding Cha modifier to initiative or as a bonus to confirm criticals.
I keep trying to think about ways to give even more uses to charisma.