The ability to stop time, I mean like everything, let it all become complete silence as everything grinds to a halt. At this point I would go to sleep and wake up with a weeks worth of sleep, afterwards I would exercise for like an entire day then sleep for about four hours again, then go fuck with all the people I hate while they can't do anything about it, like hide their keys and steal their wallets, then I would go pig out on food from the store before taking a refreshing dip in the ocean. I would want to turn time back on again of course, but it would take awhile before I got bored of having infinite time to do whatever I damn well pleased.
Although for a smaller wish I would wish for a bigger house because being able to stand up straight and having somewhere to put all this clutter would be AMAZING