A few years ago I felt kinda lame whenever I had to "make a wish" blowing out birthday candles or whatnot and the only thing I could think of under pressure was "world peace".
Since then, I've kept a wish ready to blurt out if I ever see a falling star or toss a coin into a fountain etc
For me, it's sending my mind, with all my current knowledge and experience, back in time into my body at the moment I graduated high school, so I could re-live my life with more confidence, less anxiety and get straight into doing the cool bits of my life much earlier.
On a personal level, a small house for my kids to live in before I die somewhere quiet. On a global level? Less privileged people would stop being taken advantage of by nefarious sources and systems designed to crush them.