I recently switched to a mac for my primary development machine, and I'm trying to get used to the ecosystem. Development tools, terminal tweaks and that kind of thing, but anything else that you would immediately put on a new mac.
Readit NewsReadit News
Atom: https://atom.io/
XtraFinder: http://www.trankynam.com/xtrafinder/
iTerm2: https://www.iterm2.com/
SourceTree: https://www.sourcetreeapp.com/
Asepsis: http://asepsis.binaryage.com/ (This prevents creation of new .DS_Store files - nice but doesn't work anymore with OS X 10.11)
homebrew, npm, git, bash aliases..
Above all I think the most essential tool for me is Spectacle https://www.spectacleapp.com/
Homebrew is also a requirement.
Iterm2 to replace the default terminal. I also added this https://github.com/SebastienElet/iterm2-borderless.
Everything else is pretty developer specific in my opinion. I'd recommend Visual Studio Code for a text editor (if you don't already have a preference). It has built-in git integration and installing new plugins is trivial.
Install Xcode command line tools
verbose boot messages make Library visible verify Time Machine backupshttps://duckduckgo.com/?q=setup%20mac%20for%20development
In the future if you want better help for a question like this, you should state whether you're familiar with UNIX or not, what type of development you do, what stack you develop for, what languages, what you have already done. etc.
alfred
Spectacle
Bartender
Textbar
Geektool
Xtools
Pushbullet
Mixmax menubar extension