I've decided to try playing on my new character without killing any people. I can kill animals and beasts, but no people.
As for skills, I think I'll go for these:
Two Handed Heavy Armour Alteration - Things like telekenisis, oakflesh and water breathing would be useful for this playstyle Illusion
How does that sound? Have you ever done it before?
killing people is the most fun that you are going to get out of this game, it is too bad that you can't kill everyone because some are immortal and the whole alduin thing doesn't apply to them
I had an immense amount of fun with a non-lethal playthrough of Deus Ex: Human Revolution. It's too bad there are no tranquilizer arrows or stun spells.
If you want to complete side quests without killing, I'd suggest stealth and light armor, stealth will get you to your goal and light armor will allow you to run like a bat out of hell if needed.