I have a strong moral conscience except concerning "an eye for an eye" situations. My conscience even affects how I play videogames.
I can never EVER get the evil/bad endings in videogames because I refuse to even be villainous in a game in certain parameters, as well as concerning an attachment to the world or its characters. Oblivion for example I find a very lifeless world concerning people and the fact almost everyone is an asshole makes it easier.
On the other hand, smaller worlds with personality such as Shenmue will be greatly affected and driven by my conscience. For starters when I failed to stop a soccer ball hitting a kid in a QTE I became greatly upset over the next few days. And I mean upset enough that my heart hurts.
There was also when I played The Suffering and I played entirely a good person, one example of my conscience being when I shot a tortured limbless guard to end his suffering and the game rewarded me for such, despite having no indication to give me the choice. On the other hand the game punished me for killing two monsters trapped in cages, again certain violent situations my morality becomes more darker.
Actually here's a recent example, I was playing EcoQuest, an environmental point-click game by Sierra and when the game indicated I hadn't properly disposed of the rings off a six-pack, I reloaded from my last save, went all the way up and properly disposed of them.
Yes I still have fun in Fallout 3 but I will NEVER blow up Megaton.