When I'm on Windows, I use Notepad++ but on Mac (which is most of the time), I use a Transmit/Atom combo. I'm really shallow and love the themes that I can install on it. At work, I always get asked which theme I'm using because of all the pretty colors. Plus, it's just easy to use and really customizable like TDL said. I did try out Sublime, Textmate, and VS Code but Atom is home.
If you're working in Angular 2 with Typescript, VS Code is the way to go though.