If I could have any super-power from comics, I think I'd want Multiple Man's powers. It just seems like the most effective power for a person who's not going to be fighting any super-villains; super-speed doesn't really help when you're working with computers, talking to people, or really doing anything other than running. Super-strength? Yeah, how often do I need to lift really heavy things, exactly? Stretching, flame powers...invisibility has some potential, but really, duplicating yourself is where it's at.
Suddenly money's not a problem--you can work twenty jobs, and only have one person's rent bill. You can finally sit down and really grind out levels in that MMO, because you can have one of you dedicated to doing exactly that 24/7. Reading? Watching movies? Feel free to suddenly become the most educated person on the planet, because you can read a whole library in a week. It's like suddenly having 40 times as much free time.
Not to mention you always have someone intelligent to talk to.