I'm inherently good, as befits my own personal morals, but I also tread the grey in certain situations.
For example, in Fallout 3's "The Pitt" DLC, I actually side with Ashur over Werner for multiple reasons, including trust, family values, and the handling of the cure. There are also games where I favour the darker side. Besides picking Sith in any Star Wars game, I also find that Dread is much more pragmatic than Chivalry in "Medieval 2: Total War".
I can't really think of anything other examples at this time, but I will say that some games have evil choices so distasteful or "stupid" in my eyes that I can't bring myself to do them. I definitely prefer good overall and in games where alignment doesn't really matter, like in Dragon Age, the deliberate act of being evil isn't even a matter of consideration.