As a day to day Python and iOS developer, I’m using a lot of tools on my Mac, here is a list that could help you too.
Textmate 2, Free, it’s funny to see that most people don’t know Textmate 2 is open source and totally free, this is a wonderful editor with completion and support for most languages.
SublimeText 2, free/pay, I’ve switched to Sublime mostly for the Golang support with Gosublime and not regreting it. It’s my editor of choice for almost everything now.
Colorsnapper, 5$, is a color picker, that can produce CSS RGB code, UIColors .. in your clipboards.
XScope, 30$, it’s a multi purposes tool but the measure tool is the killer feature it can measure everything on your screen (using color recognition), has also a mirror iphone app to see your design live, rulers … Useful to track mistakes from your designer.
Skitch, Free, it was a killer app until evernote acquires this company, Skitch 2 is a mess, but the app helps a lot, capture a region of your screen, share it with a link to your designer/devs … Some of my buddies are using CloudApp to do the same.
Developer color picker, Free, A custom color picker designed specifically for developers. Currently supports NSColor, UIColor, CGColorRef, CSS and HTML styles.
Google Drive, Free, You probably knew it, but many don’t know there is a native sync app exactly like Dropbox. I’ve switched from Dropbox to Google Drive: all documents in one place, complex documents editor and cheaper than DropBox.
AppCode, 99$ yearly, If you are developing for iOS, try the 30 days demo, it will blow your mind, this editor is smart and really help you, show you missing translations, show you missing @2x images, totally customizable, Jetbrains knows what is an editor, this is what XCode should be.
Since Apple is pushing the use of XIB and Interface builder, I don’t recommend AppCode anymore, but still a great product.
Paintcode, 99$, Draw rectangle, beziers path, fill it with gradients, Paintcode will generate the Objective C code for you. It can be a real saver if you have a lot of custom drawing in your app. An optionnal PSD import is available in app purchase for 20$, works well but don’t expect to much, it will help you not code for you .
Tower, 40$, Git is nice, but when it comes to fast forward your cherry pick, you propably need help (or avoid git and use mercurial which has normal messages), tower is a nice interface to git.
P4Merge, Free, A visual merge tool from perforce, that you can use with git.
Pycharm, 99$ yearly, I’m used to vim or Textmate for almost everything but as with Objective-C, Jetbrains is doing an incredible job in the Python ecosystem, supporting Jinja2 templates, Google App Engine or Django, this is my default editor in Python, it’s worth it.
Objectify, 5$, Give it a JSON, it will generate Objective-C model, to be honest I’m not using it but it may help.
Sketch, 50$, It’s a recent acquisition, Sketch is a vector graphics editor, it was primary for me a solution to open PSD, it works but you can only export with it (wil generate iOS @2x for you). What is incredible with this tool? I’m not a design guy and don’t know how to draw, everything I do with Photshop is ugly but I’m able to draw shapes usable in my work with Sketch ! This is totally new to me, this is the right tool for me.
Gimp, Free, Since Gimp is native on OSX, it’s totally usable but the PSD imports is messy. (PSD seems to be the ugliest file format in the world), Pixelmator is an option but again PSD import miss a lot of functionalities like effects.
NSLogger, Free, It’s is a high perfomance logging utility which displays traces emitted by client applications running on Mac OS X or iOS (iPhone OS). It replaces your usual NSLog()-based traces and provides powerful additions like display filtering, image and binary logging, traces buffering, timing information, etc
HTTPie, Free, Command line, cURL for human, debug REST API, test your webserver, this is what you need
Flu.x, Free, As a developer you are working late, it will change the color temperature of your screen according to the time of the day, think about your circadian rhythm.
Dash, 6$, Search inside documentation for almost everything, Cocoa, js, python … Really fast and has plugins for Alfred !
You probably have understood, I like Jetbrains products, AppCode & PyCharm, there is a Java for Android free community edition of IDEA, what I like too for this editors is the possibility to use the same colors everywhere thanks to Solarized, I’m used to Dark Solarized in XCode, iTerm2, Jetbrains products and Textmate2.
There are a lot more tools for developers on CLI but this is the my main list !
EDIT: updated on August 9th 2013