Everyone has varying strengths and weaknesses. Think hard on yourself and see if you can pick out your greatest and worst attributes?
Honesty with thyself; the greatest revelation of all.
I'll begin with:
My best attribute: my empathy. Being able to understand the feelings and motives of others is remarkably insightful, makes me a better person, and helps me relate to those whether I like/agree with them or not.
My worst attribute: my fear of failure. It prevents me from doing what is necessary in life to be the best and happiest person I can be. I don't know that I'll ever overcome it, but I'll never stop trying.