What is your favorite dev tool?

Us developers love our tools. Sometimes knowing your tool of choice inside-out can give you an 'unfair' advantage.

While I understand that a tool isn't everything, I'm always looking for a tool that can improve my developer workflow.

Currently, I'm really liking using (Neo)Vim. I like the fact that I can customize it exactly as I want it, although I understand why its not everyone's choice, and that's okay.

So what's your favorite tool? It could be anything from a simple bash script to a full package management system.

This post is not meant to say that one tool is better than another, to each their own. I want to know how your favorite tool helps improve your workflow