I'll second AI for healthcare. Medicine is the killer app for AI, and yet not nearly enough people are working on it. I suspect it has something to do with the

I'll second AI for healthcare. Medicine is the killer app for AI, and yet not nearly enough people are working on it. I suspect it has something to do with the relative difficulty in accessing data (although this is changing), and the relatively lower pay compared to working at Google, Facebook et al. But in my opinion, if you're the sort of person who's searching for meaning and opportunity, this is the place to be. Full disclosure: I work in AI for healthcare.