I'd LOVE to have someone discover a "repulsive" force in nature that could be harnessed. I am damn sick of having to set off explosions under my ass to fly into space while all the science fiction stories have spaceships that float quietly into the sky like hot air balloons.

I once thought that maybe there might be some form of matter with "negative" gravity that repels normal matter (like Cavorite). Unfortunately, anything like this formed in nature would have fled to dark spaces equidistant between galaxies billions of years ago. And I've never seen anyone mine rocks that fell up.