INFP? INTJ? I take it these are personality types? And yes, actually, I was digging through some old posts and I noted that you seem to think fairly similar to me, only you articulate your thoughts differently. Been a while since I've done a real personality test, but I vaguely remember seeing something like that.
I have seen Trigun, and I have to agree with you there. It is one of the better animes out there. I think the best of them tend to do a lot of morals and moralistic stuff.
When I write or roleplay, the characters are always realistic. They just have realistic morals, will betray them realistically, try to hold to them in a predictable way. As far as writing goes, I am good at three things:
1. Character developement, personality and stuff like that.
2. (Kind of ties in with 1) Inner drama scenes.
3. Action scenes.
I'm not so great at dialouge, but I'm working on it.
A few of the ethics I listed came not so much from my own behavior as from others. I know a lot of people who act certain ways and I think, "I'd never do something like that." For example, today, a girl in my school was telling me that she was Wiccan. She was explaining a little about it to me and another kid. Well, she was explaining about the Tarot cards, and how they work (reading the future) and the kid says, "Cool! Can I see them?" She tries to explain why nobody else can touch them. I help out here, because she's kind of at a loss for words. I say something along the lines of, "Tarot cards work by getting used to your soul, your spiritual energy, and if someone else uses them, it kind of messes them up and messes up your progress with them." I'm not Wiccan but I know a little about it. The girl agrees with what I said, and offers to read the kids future for him. As soon as nobodies looking, he grabs her Tarot cards and starts looking at them. Btw, she predicted he'll die within a week. Interestingly enough, I know a little bit about palm reading (I know which line is which and that's about it) and his lifeline ends in the middle of his hand. I guess I'll have to wait and see.

You are right that ethics is a life journey. I merely attempted to define the ones I was fairly sure of and I did say I probably missed some.
And yeah, roleplaying the bad guy can be fun sometimes, as long as you know WHY you are doing what you are doing. Ex: (from penny arcade)
Guy #1: What are you doing?
Guy #2: Killing this guy with an ice spell.
Guy #1: Why?
Guy #2: Because he's immune to fire.
People like that bug me.
I will also probably roleplay a "darker" character who does the "eviler" quests some time. However, he'll have a reason to be evil.
FYI, most of the time I try not to play characters with really "dark" pasts, especially in roleplays. While it is fun sometimes, everyone does it, and that makes it boring.