The Presence visits you in your dreams and says you can have one power of your choice (nothing too amazing however) with the catch that you must spend your life using your abilities for good or for evil.
I would pass up the opportunity to be quite honest. In a lot of ways, gaining superpowers is like winning the lottery, you think all the issues in your life are now solved, but they aren't. Instead, things become a lot more complicated and all your old problems are replaced with new dilemmas, some of which have dire consequences. Maybe if you were very poor or have nothing to lose, it would be a massive upgrade, but for most people, you will probably be in over your head and ruined all your past relationships.
When Spiderman said "With great power, comes great responsibility", he wasn't joking.