As an iOS dev, whenever I get a new dev machine, I need Xcode, homebrew, rbenv (many iOS tools are written in ruby), and some kind of extra code editor (currently I use Sublime).
But, there are a few other things that I find really help me be productive.
#1: RescueTime: https://www.rescuetime.com/
RescueTime monitors the time you use any app or website. Then, it categorizes your time based on what that app or site is usually used for (and is very customizable).
I monitor my own productivity to make sure I keep myself honest. This is because I think of my dev machine as factory equipment. If I find that a site is distracting, I add it to SelfControl (next tip) or to the hosts file directly (depending on how bad it is).
#2: SelfControl: https://selfcontrolapp.com
This app temporarily blocks websites by editing the
/etc/hosts file and reapplying the change if you reverse it. Of course, you could stop it if you want, but it's enough to augment your willpower. What do I block? All social media, but also anything that I personally visit when I want to be coding.
Over time I just added many of these sites to my
/etc/hosts file permanently.
I elaborated on SelfControl on my personal blog.
#3: Pastebot (or any clipboard manager): https://tapbots.com/pastebot/
and Windows (thanks xz) clipboard only has one slot—if you copy twice, you lose the first one. With a clipboard manager, you keep as many copied things as you want (and can easily manage, search, and paste from it.)
#4: gitprompt / bash_completion (install via Homebrew): https://github.com/magicmonty/bash-git-prompt
I use git mostly from the command-line. These tools allow me to have a custom (informative) shell prompt that shows the git status/branch and completes common git commands.
I constantly need to convert, resize, or otherwise edit images. This allows me to script them rather than do what I need manually in an image editor. I also frequently post small animated GIFs of my work in Slack or in pull requests (for those that need a visual)—gifsicle/ffmpeg let me easily resize/resample them to keep their size down.
Honorable mentions: Keyboard Maestro, Gimp, Sourcetree
What do you use?