I'd have to say that my sin is definitely lust.
To be honest, the seven deadly sins were just a device engineered to make us feel bad about being human and constantly seek forgiveness for the nature we were born with.
I don't see the problem in having a little sin in your personality. Or even a lot of sin, provided that it doesn't hurt anyone. We live in a world of consiquences rather than morality so it's down to the individual to decide if they can live with the effects of their sins on their lives.
At the risk of being flamed by the religious community, I very much doubt any sort of supernatural judgement waiting for us at the end of our lives. Even if there was, we could all just argue that our hypothetical creator made us this way. The judgement comes from other human beings who must choose how to treat you to best benefit themselves. If you're an unsavoury character then be prepared to mix with other unsavoury characters and be always looking over your shoulder or be very lonely. On the other hand, I know of a lot of celebrities and businessmen that have tactically exploited their sins for fame and fortune...
The same goes for the seven heavenly virtues. Yeah, people may love you and come to your aid when you need it, but you also run the risk of wasting your time, money and effort on people who seek only to exploit you.
In the end we're just animals trying to survive. We only live in communities because it's safer and easier to live that way. We only treat other people right because it becomes easier to live in communities if we all do so. As we were evolving, many of our sins became our tools of survival.