Every question an interviewer asks has one purpose, to see how you will respond. Your job is to mold that question into an opportunity to tell them why you will be a great doctor. You do this by showing you understand what the profession is all about, proving to them you are capable, and showing you understand macro issues like the healthcare debate. Note that they may never ask you these questions, but expect you to answer them conscientiously or unconscientiously. With that in mind, why would you want to give them a weakness or a blemish in your past? Even if they ask for a weakness you find a way to make it your strength: sometimes I work too hard and don't balance the other areas of my life for instance. Here would be my answer to the accomplishment question. Note that this is my life experience but you get the idea: I had the opportunity to coach underprivileged athletes on a basketball team that I formed for them. I learned immediately that finding ways to provide for underserved populations taught me resourcefulness, etc........ After years of hard work, 3 of those boys received scholarships to college and all graduated high school. This lesson taught me perseverance and the satisfaction I get from helping others. I also came to realize that helping others is hard work and comes without thanks many times. However, this desire to help others is what drives me to want to become a physician. (please note that this would be more thorough and well articulated if not for writing on a broken iPhone! Anyways, you could even slide in a comment about the school to open up questions about that.(which hopefully you prepared for) for instance: this experience organizing a basketball team required the coordination of parents, gyms, tournament directors, and players among others as well ad the ability to raise financial resources for the team. I learned invaluable leadership skills through this opportunity that I hope to continue to enhance at your institution. (of course that school would have in it's mission statement leadership)
Hope that helps!