I liked answering this question by emphasizing things that I loved that could not be captured on paper. Some examples :
1. Volunteering - at most you can add a couple of examples on your resume but I had been doing many activities throughout my life and this question helped me address it in detail and in a structured way
2. Passion for a unique activity - For me it was championship ballroom dancing, there's a myriad of other ones you can talk about
3. Impact of your your initiatives at work- You can talk about interesting projects you did on your own in your internships that had a great impact on your team (e.g., automating redundant work)
4. Relevant academic achievements - e.g., publishing research papers in journals, or being a valedictorian etc.
Things to avoid
1. Things on your resume (it's obvious but it happens)
2. Personal achievements (weight loss, traveling a lot etc.)
3. Things part of routine expectations - e.g., classwork assignments, normal work as part of your internship
Hope this helps,
Udayan