I honestly love this question! This is your chance to shine!
I would say it's a combination of "Resume Walkthrough" and "Greatest Strength"
Honestly, what comes to mind when you think of you? What do you really want them to know? That you're a polygot? That you love model planes? That you're super passionate about making a difference in the world?
Tell them what genuinely pops into your head! Then, make sure to emphasize slash tie it back to why you're a great/exceptional/interesting candidate!
My personal answer would be that I absolutely love learning about other people + cultures. It's why I've lived around the world and speak 4 languages (all with a terrible accent). I think this allows me to really see every perspective to a problem/situation which really helps me to help clients, solve problems, and work well in teams.