In Dragon Magazine 404 (4th edition), there is a rules supplement covering exactly what you are looking for: Unearthed Arcana: A Matter of Honor
The article presents different ways to implement honor and different styles in which it can be presented such as "Thieves' code", "Bushido", "Chivalry" and "Harper's code." If you implement the Honor code system players will be required to take 1 feat. They have about 4 feats to it as well.
If your DM decides to add honor as a game element
to a campaign, you can use this system by choosing
an honor code or making one of your own. If you do,
you take the Honor-Bound feat. This uses up one of
your available feat slots, so if your character is above
1st level, you must replace one of your existing feats
You adhere to an honor code. In sticking to this
defined morality, you gain a spiritual advantage akin
to good luck. This kindness of fortune is most powerful when you act honorably.
Prerequisite: Must have an honor code
Benefit: You gain 3 honor points and the honor-able action power.
You rise to the challenge when honor is on the line.
Encounter No Action Personal
Trigger: While acting honorably or
avoiding dishonor, you make an ability check, an attack roll, a damage
roll, or a skill check and dislike the result.
Effect: You spend 1
honor point. Roll 1d6 and add the result to the triggering roll.