There is a chart in I hate you--Don't Leave Me that defines Personality as a series of intersecting lines. Each line represents a personality trait, and where it is intersecting is where the individual lies on that trait's continuum. I couldn't find an image, so I replicated it in Google Docs (Have I told you that I'm obsessed with Google? I am.):
According to the above chart, this person is a compulsive dieter, who is afraid of commitment, and a little selfish, but otherwise fairly balanced. Did you see that?
I like this because it presents the traits as a continuum. I also like the control it conveys to people. If they want to change a certain trait, they can with work, by making conscious choices in the direction they choose. It is easy to understand that everyone is unique. It is also easy to see that people would react differently in similar situations.