Desktop
Emacs
The editor to end all editors. Or the OS in need of a good editor, depending who you ask. Editing modes for every language, markup, conf file out there.
org-mode
https://www.youtube.com/watch?v=oJTwQvgfgMM TODO lists, GTD, hierarchical notes, et al.
Improved puppet-mode
https://github.com/ilikejam/puppet-syntax-emacs/commit/133afcd48f4e7188561981072c19c57644c1eb0d Now apparently superseded by a different module, but if you like the original Puppetlabs mode there might be some nice changes in my patch branch
rainbow-delimiters
https://github.com/Fanael/rainbow-delimiters Subtle colour hints for brackets etc.
Config
https://github.com/ilikejam/Environment/blob/master/OSX.emacs
Shell
Terminal (OSX)
The default terminal app on OSX is Just Fine. Even does middle-click paste.
urxvt (Linux, Windows)
https://wiki.archlinux.org/index.php/Rxvt-unicode Fast, unicode and TT font support, resizing works. Most of the time
bash
https://github.com/git/git/blob/master/contrib/completion/git-completion.bash https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh
Airfoil (OSX)
https://rogueamoeba.com/airfoil/ Send audio to chromecast, airplay, and bluetooth from individual apps (or the system) to multiple sinks. Combine with Chromecast Audios (sadly discontinued now) for dirt cheam multi-room audio.