I'd have powers like Nova from the Marvel comic series:
"Nova derives his powers from an energy source called the Nova Force which all Nova Corps Centurions wield. This energy was transferred by Xandarian technology to Rider by the Nova-Centurion Rhomann Dey. Nova's small measure of the Nova Force gives him superhuman powers including flight, superhuman strength, speed, and durability, as well as the power to absorb energy directed against him and release it as gravimetric pulses and beams, either from specific parts of his body or from his entire body."
I thought about reading/manipulating minds, but that would just lead to becoming callous to the entire human race until the day I died.
I thought about going back in time, but there's no guarantee that I would change anything or live forever.
So I want to be indestructible, and be able to fly throughout the universe. It's ever-changing. Who knows what lifeforms are out there? I could witness the entirety of the human race, and everything else too.
The power to make all women in the world orgasm at the same time. A mass orgasm so powerful it will shift Earths axis and will bring another ice-age and males will no longer be frowned upon for wearing uggs. True story.