God, where on earth would I start? I'll say one thing now and then think of 20 others as I try and fall asleep tonight. But if I had to choose one now, I'd probably make world travel more accessible; probably through teleportation or some technology that only really exists in Star Trek. I think experiencing other cultures expands your mind and helps build empathy. Travelling is something that has changed the lives of pretty much everyone I know, so I think the more people who got to experience that, the better off we would be as a planet.
Then again, it might just make popular destinations even more overcrowded with tourists, so what the hell would I know? I just want teleportation, dammit!