Demonic Sneak Attack( Fiendish Codex I: Hordes of the Abyss, p. 85)
You know exactly how to twist the blade to get the most out of your sneak attacks.
Sneak attack class feature,
When you make a successful sneak attack, you can reroll a number of sneak attack damage dice equal to the number of Abyssal heritor feats you possess. You must take the results of the rerolled dice.
You trade feints for finesse and find it difficult to hide your more malicious intentions; consequently, you take a -2 penalty on Bluff checks.