From what I have seen on these forums, it seems that playing an evil character in a game is almost unthinkable. I am confused by a lot of the recent threads. When I play a game I feel that I am playing a role that has been placed in front of me. That may be the role of a great hero, or an unsavory *bleep* saving the world just because.
I've been playing a pathfinder game where my character is evil and is serving evil. I don't have a problem with it. The DM has provided a story where there is a greater evil that the group has to stop. I know that sounds like my previous unsavory *bleep* comment, but it is much deeper than that.
In my character's back story I have done things that seem to be taboo. He completely destroyed his home town, children included. He raped females of the caravans he raided. After having his mind invaded by Tiamat he wasn't a nice person.
I have fun playing this character. I would say that I've had more fun playing this character than any of the goody goods that I have played in the past. I may be trying to save the world, but I don't have to be nice about it.