How loose is the definition of "magic" here? can I wish for "Control over all of reality"? I wouldn't but just asking.
I'd like some form of mind magic. Telepathy, thought reading, mental suggestions, mind empowerment that sort of stuff. Astral projection might be cool as well. Any number of those, I suppose.
Alternatively, time manipulation. Although, as a person who has been interested in magic for a long time (in fantasy, of course) I know how bad that could be. With this in mind, I wouldn't want to cause any paradoxes, so 1. it's just localised time manipulation (myself, a person, or a small area, that sort of thing) and it would just slow down/speed up the thing manipulated.