The short answer is everything. The long answer is an exhaustive list of frontend and backend languages and protocols. I've actually bookmarked this link and aim to set it to memory:
I will be basing the list off of three things:
A combination of what most programs in 2017 are teaching students.
My own personal experiences from interviewing at companies for developer positions in the past and also interviewing potential candidates for current Full-Stack Developer positions at my current company.
Stories and feedback from people on Coderbyte who have been accepted to coding bootcamps and then proceeded to get programming jobs.