You could say "Myself" or just give your first name.

If someone to ask me to describe myself in one word, I would say "Compassionate" which also means caring... Depending on where I am and how I am feeling I might use a different word. Like in a job interview I might say "Passionate" OR "Target driven" OR say "Hard working". So basically when someone asks you to describe yourself in one word, they are asking to describe your personality in 1 word. AND I beleive this kind of question is stupid coz we human beings are capable of so much.. You just can't describe a whole person in just 1 word.... I have some good ones. I am "Extra ordinary", "Original" ..... Hope this helps... :D