I'd give myself superhero-class goals to accomplish, and varying powers to accomplish them with. Starting with "Stop that speeding train with flight and super-strength" and "Solve the middle-eastern peace problem with the power to spread universal love", and progressing in difficulty to "Solve the middle-eastern peace problem with nothing but super-strength" and "Stop that speeding train with HEART".
Or, uplift a few chosen people to my power levels -temporarily- and let them compete to see who can accomplish these tasks first...or cooperate to try and beat a high score.
Mostly I'd want to tweak other people, though. Not directly or anything. I'd want to make little changes to help people reach their full potential. Use savestates and min-max the world. Hell, see how much I can manipulate the butterfly effect. One thing I've always wanted to do, actually, is have enough precognitive and psychic power that I could know how people would react to anything I could possibly say, and use that power to manipulate geopolitics while sitting in my room on a cell phone. How many phone calls would it take to bring about global catastrophe or world peace?
Maybe I'd have to mess with some Dark City kinds of things, though, just mucking with peoples' surroundings and memories while they're asleep to see what happens. Or, what would the world be like if everyone could fly? Even cooler, though, would be "What if every scientist and every engineer got funding and support for whatever they wanted to work on". Maybe I wouldn't directly bring about the End of Scarcity, but I would let people have any job they wanted. With that much science "funding", I bet that after thirty years they wouldn't even need my help any more.
I'd create Valhalla, because that sounds like a great place to visit.