Welcome to HN!
Here's my favourites, I won't drop any links as they're all pretty easy to find and it's not all Mac specific.
* Alfred - It's like spotlight on steroids. Bind it to cmd+space and you're a tap away from everything on your computer. The powerpack is worth it.
* Sublime Text 2 (using 'Made of code' theme ('Tomorrow Night' is also nice), with JSHint and some other plugins)
* Sparrow (for email)
* Sketch (vector graphics) - It's not quite good enough to replace the Adobe suite but it's getting there! Great for mockups.
* Mou - Markdown Editor.
* Virtual Box - With the free IE VMs from modern.ie
* ImageOptim - Little tool to optimise images.
* CodeKit - I use this for simple sites - It compiles CSS, JS, HTML, etc from pre-processors and template languages as you work. I've found it has some performance problems but still quite handy.
* XScope - Various tools for measuring things on your screen. Really helps if you do a lot of PSD to HTML work to check everything is pixel perfect! It also has an iPad app which mirrors photoshop or your display to the iPad screen.. not terribly useful but cool none-the-less!
* Littleipsum - Menubar item to generate Lorem Ipsum
* iStat menus - Menubar addons - Provides a nicer clock and various performance monitoring widgets.
* 1password - Now I have a unique, long and complicated password for every different website and I don't have to remember them!
* Keka - Decompress all the files.
* Onyx - Preference Pane with various tools for system maintenance
Quicklook is also quite useful, press the spacebar on any file to see what's inside. There's some tweaks you can do to get the most out of it:
* Enable text selection (type in terminal):
defaults write com.apple.finder QLEnableTextSelection -boolean YES;
killall Finder
* Keep quicklook open when you switch applications (type in terminal):
defaults write com.apple.finder QLHidePanelOnDeactivate false;
killall Finder
* There's plugins for loads of additional file types, but I like this hack to preview any file as plain text:
https://coderwall.com/p/dlithwStuff for the terminal:
* Tomorrow Night theme
* Homebrew - apt-get for mac.
* ZSH + Oh my ZSH - ZSH is a great bash replacement and Oh My ZSH adds a lot of useful stuff. I epecially enjoy the git integration. My prompt looks like this: "➜ dirname git:(master) ✗" (the X means I have uncommitted changes)
Ehhh I think that's about it!