There are some people the world is legitimately better off without. Death may be a bit much without any warning, but since I'm allowed to write in the details, it'd be easy to give them a wake-up call then give them some more time in this world to right their wrongs, exact time (if any) depending on how shitty of a human being they truly are. I'd have to start with the worst of the worst (a certain "music" icon comes to mind, but shall remain unnamed) and from there filter out who does or doesn't get their lives back on track. If they're just going to be douchebags to everybody else and waste their time getting into trouble and drug scandals, are they even living to begin with?

I wouldn't say I'd re-shape the world, though. Simply pick off a bottom rung, based on what I know instead of what I think. That, or I'd use it one time then never touch it again. Maybe use it one more time when I'm older and ready to go the way I want to.