I would manipulate historic events, including preventing the extinction of Dinosaurs, to place me as dictator of Planet Earth. I will then rule with a might fist and having an army of Dinosaurs enforcing my will.
Travel to future, acquire cures for everything. Travel to past, give them to myself as a child.
Spend rest of life doing whatever I want without consequences. Why yes, I *would* like to try all 67 flavors of your ice cream while I sit here relaxing instead of exercising ever.