If a project has a more complex build, gulp allows us to build a flexible build pipeline and automatically rebuild on files changes. Speeds up JS development. gulp
Writing README.md's is very important to us. Also a lot of our content is maintained in Markdown (using contentful.com). We are also cool with org-mode. Markdown
Sentry is amazing, most of our systems send their exceptions to sentry. We couldn't live without it and get a much better understanding of how our code is behaving in the wild. Plus it integrates with Github. Sentry