There are probably huge strides that can be taken in healthcare, food, energy, transportation and finances. The challenge is that most of these industries are heavily regulated so you go in optimistic then get inundated with endless waves of bureaucracy, and end up making a new version of Twitter.
I'm personally fascinated with the transpiration industry. Everything from city bikes, to self driving cars, to hyper loop[1], to super sonic transport[2], to intergalactic transport[3].