Many RPGs and LARPs have systems for ethics. Many do not. The ones that do not allow players to avoid the IC moral implications of actions, especially murder, and I feel that that cheapens the role-playing experience, whether you're playing D&D or the most refined LARP.
Ethical systems in games are often clumsy and awkward, and hard to use properly.
Here're some examples:
Humanity (and all the other Path traits) in Vampire: The Masquerade
Sanity in Call of Cthulhu (actually, this only applies to really heinous acts, so it's not directly an ethical system)
Mental Balance in Kult (long time since I read it, though)
Good/Bad/Neutral Stuff in Amber DRPG
Humanity in Cyberpunk 2020 (debatably an ethical system)
Wraith's Shadow system (forget what it's called)
Rage in Werewolf: The Apocalypse
Banality in Changeling (banality makes you more callous, so like CP2020 it's not really an ethical system)
Alignment in D&D
Karma in Shadowrun (at least it worked as an ethical system in 2nd ed.)
If you had to write a system for ethics in an RPG - either an existing one or your home brew - how would you do it?
Would the Ethics trait actually affect game play?
Would it be rolled or just automatically deducted?
Would the GM control it, the other players, or would you trust the player him/herself?
Are there roleplaying consequences (like Frenzy in V:tM or Cyberpsychosis in CP2020)?
Are there stat changes (or even bonuses/incentives) for being more or less immoral (like in Wraith or Kult)?
Would it be a slippery slope like Sanity, where it gets easier and easier to lose levels of the stat, or a slow fall like Humanity, where you have to basically rape several nuns while microwaving live babies to lose the last point?
Should players be able to customize their moral system, like in D&D, so that for some, getting an abortion or cheating on your taxes is immoral while for others, you have to kill or destroy to even start to care?
Or should it be hard an fast, where even killing an enemy trying to kill you in the heat of passion calls for a trait loss or such?
How would it work, in general?
Have you tried one out?
Do you have a favorite published system?
And what games is it appropriate to have an ethical system? I assume it's unnecessary in "Beer & Pretzels" games like Toon.