What are some of the not-really-famous JS libraries that you use on a daily basis?

Everybody who is into JS knows about React, by now. The other day I saw someone here share this scaffolding tool, Slush, that I've never even heard of. And it looks awesome.

I am curious to know about a few JS libraries/tools that a few of you might be in love with, but still not as popular in the JS world at large.