Atom 

I’ve been a fan of Atom since its early releases. It’s a code editor, so if you never edit HTML, JavaScript, CSS, Python, R, or any other programming or markup language you probably have no use for it. But it does its job well.

Because Atom is built on the Chromium codebase and uses familiar standards like CoffeScript and LESS, it is easy to configure and extend for experienced web developers. For example, changing the color of a syntax highlighting rule is a matter of writing CSS (LESS).

The best part of Atom is also its biggest weakness: extensibility. Atom uses a package manager built on top of npm, and it has a built-in directory of packages. Unfortunately, this makes for a somewhat nightmarish “preferences” dialog, where hunting for the right place to set a checkmark can be a frustrating exercise. Fortunately, Atom has a large userbase, and if you encounter a problem, there’s usually someone else who’s already run into it and found a solution or workaround.

I’ve not found the autocompletion features as useful as those in more mature IDEs, though the packages around this functionality are continuously improving, as well.