Front End State of the Union, 2016: Best Practices a La SASS, ES6, React, Etc.

Would be great if we could discuss the 'State of Frontend' as of April 2016.

My suggestion is that all contributions aim at breaking their responses as follows:

1. Cutting edge - Stack of choice; examples, links would be nice.

2. Pragmatic usage, currently used in production. Stack of choice, examples and links welcome.

Thanks!