It's a tough question because I can come up with more than three. But here are the top three:
- Problem solver
What about you? Try doing this for your characters. I've found that it forces me to think about my characters more deeply. For example, if my character is a problem solver he should be able to get out of whatever situation I place him in. If he needs a bridge and doesn't have a bridge he'll figure out how to build one.
So, what are the three words that describe you and/or the protagonist in your story?