Anyone familiar with Scion, White Wolf's game of modern epics, will find this familiar.
I've always liked the idea of a mechanical means of handling beliefs and alignment, and I've found the virtue system to my liking. Any virtue can be used to help accomplish goals in line with it (for example, those with Valor could use it while defending the helpless), but also includes a short list of no-nos. Sinning against your Virtue requires failing a Virtue Check to allow the lapse in belief; if the character succeeds instead, he suffers a Virtue Extremity as he tries to atone for considering violating his beliefs.
Scion uses a d10 system, so it can't be used as originally written in a traditional D&D rule set... my 2e version basically treats Virtue Points like HP or PSP totals. Spending a Virtue Point allows the player to add a +1 bonus to any die rolled in line with the Code of his virtue, even after the die has been rolled (useful for surviving those failed fatal saving throws!). Virtue Checks work like any ability or proficiency check. In 3.X, I recommend a check at DC 20. Checks are always made using the maximum, not the current Virtue Points.
In Scion, a character has four Virtues; this number could be reduced depending on a DM's tastes, but in the interest of playability, I don't recommend increasing it. As far as the number of points in a given Virtue, my recommendation is 1 point in each of the four, and 3 + Wisdom saving throw bonus (2e) or Wisdom modifier (3.X) points to distribute between them.
Virtue maximums and increasing them are matters of the DM's taste. I'm thinking level + 3, add a point to one Virtue every level and as a reward for good roleplaying (using the guidlines for belief points from the PWHB).
Without further ado, I submit the sixteen Virtues from Scion. Let me know what you think.
The Code of Ambition I will fight against anyone who threatens my goals I will defend valuable servants or pawns I will risk anything in pursuit of personal power I will seize any opportunity to weaken a rival
Sins Against Ambition I will not demonstrate compassion when it would place me at a disadvantage I will not refuse a risk that is outweighed by its reward I will not miss the opportunity to usurp another's authority
Virtue Extremity: Overweening Arrogance. The character becomes so consumed by his own sense of superiority that he fails to see the limits of his power. He refuses to show respect to all but the most dangerous of superiors, and he puts his own lust for power above all other goals. Lasts for one day.
The Code of Conviction I will win converts to my cause whenever possible I will resist any persuasion or compulsion to go against my beliefs I will always determine the best course of action to benefit my cause I will, if necessary, perform heinous acts in support of my beliefs
Sins Against Conviction I will not fail to respond to attacks on my beliefs I will not act in a way that violates the tenets of my cause I will not refuse any action that would benefit my cause
Virtue Extremity: Fanatic Zeal. The character goes to extreme lengths to support or defend his cause, regardless of personal danger or suffering inflicted on others. No one -- friend or foe -- will stand in the way. Lasts for one hour per point of Conviction.
The Code of Courage I will fight against any foe, no matter the odds I will always act without fear or compulsion I will take any risk, regardless of danger
Sins Against Courage I will not avoid the prospect of a fight I will not back down from a challenge I will not surrender to any opponent I will not give aid to another in a fight, nor will I accept it
Virtue Extremity: Berserker Fury. The character is so overcome with shame at his perceived weakness that he flies into a murderous rage, hurling himself at his foes without regard to his own safety. If there are no foes left to fight, the character will attack any other living thing he can reach, seeking to expiate his cowardice in violence and bloodshed. Lasts for the remainder of the encounter.
The Code of Duty I will help those in need I will support, heal, and foster strength in my community I will uphold the laws of my community I will look to authority figures when I need guidance
Sins Against Duty I will not steal from a community I will not break a community's laws I will not defy legal authoirty I will not place personal ambition above the greater good
Virtue Extremity: Morbid Self-Sacrifice. The character is so mortified at having contemplated violating the sanctity of community that she goes to extreme lengths of personal self-sacrifice to atone for her selfishness. She might donate personal possessions or wealth to the community, break ties with her family in disgrace, seclude herself from the community she "failed," turn herself over to the authorities to confess any crimes she's committed, et cetera. Lasts for one day.
The Code of Endurance I will always act without fear or compulsion I will endure pain, hunger, thirst and fatigue
Sins Against Endurance I will not fail to act because of risk to life or limb I will not rest in a time of crisis I will not avoid a course of action due to injuries, fatigue or lack of resources
Virtue Extremity: Self-Destruction. The character is so horrified at her own weakness that she attempts to purge it through acts of extreme self-punishment, pursuing her goals without regard to personal health, safety or survival. Lasts for one day.
The Code of Expression I will create memorable works of art I will repair or restore damaged works of art I will assist or support musical, theatrical, and other performances
Sins Against Expression I will not deface or destroy a work of art I will not refuse to create or perform a work of art I will not repress or discourage works of art or communication presented by others
Virtue Extremity: Visceral Shock. The character's extreme reaction to stifling her (or another's) art pushes her to the opposite extreme. She pours her guilt and self-recrimination into her efforts, pushing the performance into the realm of the vulgar and grotesque. She bends her energies to creating art that scars and horrifies her audience. Lasts for one day per point of Expression.
The Code of Harmony I will determine a balanced solution to problems I will act in ways that maintain or restore balance in a situation I will always try to persuade others to alter their actions to preserve a balance of forces
Sins Against Harmony I will not knowingly create an imbalance of forces I will not counsel action that creates an imbalance
Virtue Extremity: Tyranny of Balance. The character goes to extreme measures to restore the balance of outcomes in a given situation, even going so far as to inflict harm or suffering on herself or her compatriots if necessary. Lasts for the remainder of the encounter.
The Code of Intellect I will find new solutions to persistent problems I will investigate that which I do not understand I will seek to acquire knowledge I will always try to persuade others of the ideas or theories I have found to be correct
Sins Against Intellect I will not destroy a source of information or knowledge I will not suppress or censor knowledge I will not silence debate I will not promote ignorance in any form
Virtue Extremity: Obsessive Analysis. The character's attempt to blind herself to reason forces her to atone by overanalyzing everything. She becomes powerless to make important decisions as she wracks her brain trying to imagine every contingency and every conceivable outcome from every given course of action. Lasts for one day.
The Code of Loyalty I will fight on behalf of a friend when necessary I will defend a friend who has been unjustly accused I will always aid a friend in need
Sins Against Loyalty I will not betray a friend's trust I will not refuse to answer the call of a friend in need I will not desert a friend who has been accused of a crime
Virtue Extremity: Blind Devotion. The character is so horrified by her attempted betrayal that she will go to extreme lengths to support her friend or kinsman, suffering alongside that person even if said person is proven to be in the wrong. Lasts for one day per point of Loyalty.
The Code of Malice I will fight without hesitation against any enemy I will attack the innocent and helpless to display my superiority I will torture those at my mercy I will intimidate others without regard
Sins Against Malice I will not honor a truce I will not release a prisoner from captivity I will not end another's life without causing significant pain and terror I will not ignore an opportunity to torment my enemies
Virtue Extremity: All-Consuming Hatred. The character's contempt for all life exceeds all bounds of common sense. The character cannot ignore any opportunity to inflict suffering that comes his way, even when doing so diverts him from his true goals. A character in the grip of such a hatred would delay his enemy's execution to pull the wings off a fly. Indeed, such a character might delay the execution indefinitely, stretching out his enemy's torture as long as possible even though doing so increases the chance of his enemy's rescue or escape. Lasts for one day.
The Code of Order I will investigate crimes I will determine wrongdoing and assess penalties I will pursue fugitives I will deliver lawbreakers to justice
Sins Against Order I will not commit a crime I will not turn a blind eye to a criminal act I will not allow a criminal to escape I will not bend rules or selectively apply rules to others
Virtue Extremity: Summary Judgment. The character takes the law into her own hands, ruthlessly passing sentence -- and executing judgment -- on those she perceives to be criminals. Lasts for the remained of the encounter.
The Code of Piety I will employ time-honored ideas or tactics to solve a problem I will act in accordance with the wishes of my family and society I will uphold tradition and custom over innovation I will impose the dictates of tradition on others
Sins Against Piety I will not defy the wishes of my family and society I will not break with tradition or custom I will not allow others to break with tradition I will not advocate new ideas over tried-and-true precedent
Virtue Extremity: Self-Righeousness. The character withholds her support or aid from those she deems insufficiently pious, even going so far as allowing others to suffer or die as a result. Lasts for the remainder of the encounter.
The Code of Rapacity I will fight against anyone who interferes with my desires I will avenge myself against those who keep me from my desires
Sins Against Rapacity I will not give away a possession I will not resist an opportunity to seize an object of desire I will not pass up the chance to satisfy my desires when the reward outweighs the risk
Virtue Extremity: Reckless Hunger. The character's obsession overwhelms all capacity for rational self-interest. She will take any risk to secure the object of her desire and accede to any request by one who can provide her with what she wants. Lasts for one day.
The Code of Valor I will defend the helpless I will defeat those who prey upon the innocent I will fight fearlessly and with honor I will endure pain and fatigue
Sins Against Valor I will not fight dishonorably or strike from ambush I will not avoid an honorable fight out of fear for personal safety I will not allow others to suffer the depredations of the wicked
Virtue Extremity: Valorous Sacrifice. The character is so horrified by her perceived cowardice that she must atone for her sins by seeking an honorable death in battle. She attacks her foes with no regard for her personal safety or survival, and fights until she or her opponents are destroyed. Lasts for the duration of the character's next fight.
The Code of Vengeance I will hunt down and punish criminals I will discern wrongdoing and assess punishment I will defeat those who oppose my efforts I will investigate crimes
Sins Against Vengeance I will not let a crime go unpunished I will not forgive a crime against myself or another I will not show leniency to a criminal I will not give up the pursuit of an offender
Virtue Extremity: Implacable Nemesis. The character will go to extreme lengths to punish an offender, making any sacrifice necessary -- or committing any atrocity -- in order to see justice done. Lasts for one day per point of Vengeance.
The Code of Zealotry I will fight against all enemies of my superiors I will work toward the goals of my superiors I will persevere against all odds to serve my superiors
Sins Against Zealotry I will not ignore the chance to capture or kill an enemy I will not ignore any command from my superiors I will not surrender to the enemies of my superiors
Virtue Extremity: Obsessive Mania. The character's quasi-religious loyalty to her superiors evolves into full-blown mania. The character becomes so convinced in the inevitable victory of her master(s) that she ignores obvious threats to the fruition of her plans. Whenever confronted with anyone showing disrespect to his superiors, the character flies into a rage. Lasts for one hour per point of Zealotry.
I haven't read Scion, but the idea seems similar to the Paths of Enlightenment from Vampire: The Masquerade or the Virtues of Exalted. I want to address the four I believe you've added to the list from Scion (Ambition, Malice, Rapacity, Zealotry). I assume you've added these to be more exclusive of the evil alignments or others that simply place their beliefs above the welfare of others. The problem I have with codes for evil people is that they typically aren't that interesting. They either require that the character do what they were going to do anyways or they call on the character to be outright evil for the sake of evil when subtlety would've been more appropriate.
I think the idea of virtues can work with or in replacement of alignment. I'm not sure players would find this list comprehensive enough for the variety of philosophies a Planescape character could have, but it does a good job of representing good and evil mindsets. In order for this system to be of much use, however, I think there needs to be some sort of explicit mechanic for introducing situations where the code is tested. A character may genuinely feel that the Code of Loyalty is important, but unless they are placed in situations where the adherance to that code becomes a problem and they have a genuine philosophical conflict, it's not going to matter. I would tie this system with some sort of narrativist mechanic wherein a conflict is made to arise within a certain number of sessions, or if the character is either lax or strongly reliant on the code's benefits.
-Gabriel Sorrel, www.planewalker.com