Since I just wrote about my favorite iOS apps, I had to do the same thing for Mac OSX apps too.
Before I start, it's important to note that I have super computer - a 15" quad core Retina Macbook Pro with 16 of RAM. I'm blessed to have a computer that handles all of these applications simultaneously. I don't ever close any apps. I'm always running at least 30 apps. Many are background apps like Alfred, but they all contribute to my personal computing efficiency.
Here are the apps that make my day, everyday, 10+ hours a day. Enjoy.
Adium - Adium is a cross platform instant messaging client. It hooks into Facebook, Gchat, and dozens of other messaging services. Unlike most of the other apps on this list, which value simplicity and fewer options, Adium offers hundreds of options. I've never seen a more extensible and flexible chat client. Even still, it's fast and well designed. Most importantly, it integrates Facebook and GChat natively into OSX.
Alfred - exceptional. Alfred lets you "tell" your computer to do anything. It's not "smart" per se like Siri, but it's incredibly fast and effective for personal productivity. I use it on average 40 daily per Alfred's own usage logs. It's so good, I wrote a whole post about it. If you have a Mac, download it, now.
BetterTouchTool (BTT) - exceptional. BTT understands over 50 multitouch gestures on the Mac Trackpad, and can map any gesture to any OS or application specific command. It perfects the trackpad. It's so good, I a whole post about it too. If you have a Mac, download it, now.
Caffeine - Caffeine is really simple. It lives in the menu bar, and prevents the screen from going to sleep. That's it.
Chrome - Chrome is the best web browser hands down. It is the most secure, fastest, most standards-compliant browser on the market with the sleekest UI. It also offers seamless profile sync across all major computing platforms, and has a large developer community that write great extensions. Thank you, Google.
Clear - the best task list manager. It's clean and simple. No dates, no options, no reminders, no settings. Just swipe and done. And of course, it syncs with Clear for iOS, making it a killer productivity app at the desk and on the go.
DashExpander - a very simple text-expansion tool. Type a predefined token, and DashExpander replaces the token with anything else. I have over 50 shortcuts saved, including credit card numbers, email addresses, URLs, passwords, and more. It's a very useful tool. Apparently, it's no longer available for download. I'm not sure why.
Divvy - Divvy is a great window-management utility. I use it every morning after plugging in my 2 external monitors at work. Divvy expedites the process of moving windows around, especially across 3 monitors.
DropBox - DropBox is amazing. I use it for a variety of different reasons. I have DropBox set as my default download folder, meaning that I can download a file and walk out the door and know that the file is immediately available on my iPhone. I use DropBox as a personal FTP server. I use it to sync pictures from my iPhone back to my Mac. It's a fantastic utility in many respects. In 10 years, we will look back at DropBox as one of the defining applications of Post-PC era because it powers cross-device and cross-platform computing.
Evernote - I use Evernote to remember everything across all computing platforms. I sync tons of content to Evernote on a regular basis. I love it.
Fantastical - Fantastical provides the best UI to add calendar appointments on the OSX. After clicking Fantastical in the menu bar, I can just type the event description as a statement. For example, "Dinner with John at Chuy's Thursday at 9." Fantastical uses Natural Language Processing (NLP) to create calendar appointments on the fly. I don't ever click through date/time pickers, add attendees manually, or set locations via disparate controls. I write a brief statement, and Fantastical does the rest. It's like Siri for making calendar appointments, but without voice-to-text.
iA Writer - I use iA Writer to write and blog. It offers a clean and elegant UI that allows me to get in the zone. Focus is about saying "no", and iA writer understands that. There are no distractions and very few options, settings, or preferences to get in the way.
join.me - The easiest to use screen sharing utility. In one click, join.me begins sharing the screen and generates a unique session number to give to others. 1-2 more clicks to email a link. Simple, easy, awesome, and free.
Kindle - Kindle is the best eBook platform. It has the largest library of books at the best prices, supports all major computing platforms, and offers great digital-only features that enhance the reading experience like dictionary, highlighting and note syncing, X-Ray, etc.
Kod - Kod is just a text editor. It doesn't have many fancy features, but it's lighting fast, and has a UI that's inspired by Chrome. That's all I need from a text editor.
Mail (Apple) - Apple Mail is the best Exchange client I've ever used. It offers a UI that makes it much easier to parse and understand emails than Outlook. The animations are satisfying. The only problem with Mail is that it can temporarily freeze when it tries too aggressively to search through large contact lists. Still, it's better than Outlook for Windows or OSX.
MenuMeters (screenshot below) - I shouldn't use MenuMeters, but I do. It would seem hypocritical of me to talk so much about simplicity in computing, then go out of my way to illuminate all of the technical complexity of computing at all times on my primary work machine. I would really prefer not to use MenuMeters, but I need it. I only use the features that graph CPU usage and real time upload and download rates. The CPU graph highlights which applications are computationally intensive, and the upload/download rates indicate if network connectivity is as fast as I think it should be.
Messages (Apple) - The default messaging solution on all cell phones is still the ancient SMS text. Apple co-opted SMS with iMessage on all iDevices, making it easier to text my friends. Since most of my friends have iDevices, I receive their text messages on my laptop while at work, even though my friends didn't go out of their way to use a non-default messaging service.
Parallels Desktop 8 - Parallels is the best virtual machine to run Windows on OSX. I generally use it all day at work since VersaSuite is a native Windows application and won't run natively on OSX. Although Parallels was less than ideal for all day use a few years ago, today it's a mature application. It's fast, and has all of the features I need to work across OSes all day everyday.
PopClip (screenshot below)- PopClip brings iOS' cut/copy/paste functionality to OSX's mouse. After highlighting any piece of text, PopClip gives a popover with a handful of options, including Google search, cut, copy, paste, and more. It's pretty sleek.
Preview (Apple) - When I worked in Windows, I had to use SnagIt to quickly take screenshots, annotate them with arrows and text and the like. On OSX, I can do that out of the box with OSX's built in screen capture tool and Preview. I use Preview to submit bugs and features enhancements to our developers at work multiples times daily. It's fast and easy to use. Sorry, no link to Preview. Apple doesn't have a webpage for Preview anymore.
Reeder - like on iOS, Reeder for OSX provides the best RSS UI to trudge through and share hundreds of articles on a daily basis. It understands its job, and does it better than any other RSS client I've ever used.
Sparrow - Sparrow is native Gmail on OSX done right. The UI is minimal and fast, and supports all of the Gmail specific functions that I need. It even auto-converts attachments into DropBox links.
Spotify - like on iOS, Spotify offers the music listening experience that Apple should. $10/month to listen to whatever I want, whenever I want, on any device that I want. Perfect.
VLC - VLC plays almost any video file ever created. No stupid codec or compatibility issues.