Firefox – I’ve used each of the three big browsers on Mac, each for quite a while. Safari is good and I love some of the system integration it offers but it lacks some advanced features. Chrome is an excellent browser but I have growing concerns about Google and privacy. Firefox is the compromise. Not quite as fast as Chrome, not as smooth system integration as Safari, but it is widely supported and has a lot of flexibility.
Airmail – Airmail is inexpensive and lets me integrate with multiple email accounts. At this time it’s what I use but I don’t see myself using it for years. The interface is cluttered and keybindings are not intuitive. It’s under $5 so you can’t beat the price though.
Adium – Are there other IM clients besides Adium? It supports everything I use, feels like a Mac app, and is in general rock solid. Maybe it doesn’t support video functions and other advanced features of modern IM protocols but that means nothing to me.
Multimarkdown Composer – When I have my choice of writing formats, I default to Markdown. It’s not perfect but it’s as close to perfect as I’m going to get. Multimarkdown Composer adds features to Markdown and provides a nice preview pane. Customizable styles and a good variety of export formats solidify MMC as my writing tool of choice.
Readkit – Newsblur is my RSS aggregator and Readkit integrates with it. If Newsblur had a native client which supported all of its features, I’d probably abandon Newsblur relatively quickly. But it also provides support for Instapaper and Pinboard; both are services I use so it would stay on my computer and in frequent use.
iTerm 2 – iTerm 2 is like the built in console but more powerful. Split screen and unlimited buffers are just the start. It’s one of the first apps I install on a new Mac.
Aquaemacs – I’ll stand by the assertion Emacs has more power than any other text editor. Unfortunately, Apple ships an old version of Emacs (22.1.1, circa 2007) with OS X. Aquaemacs adds a little bit of OS X to Emacs. It’s not perfect but provides me the power of Emacs on OS X.
1Password – I don’t know what I would do without 1Password. It is on every device I own which supports it. I’ve bought the Mac version at least twice, probably three times through multiple upgrades. There is no other application I use which would have more severe repercussions if I didn’t have it.
Alfred – Quicksilver went a long time without maintenance so I moved off it. While Quicksilver had the power, Alfred is a great compromise on power and simplicity. Alfred 2 now has workflows making complex actions possible. As an idea of how much I use Alfred, since March 14, 2013 I’ve triggered it 6,313 times at an average of 20.4 times per day. Don’t forget this is my personal machine. Another 8 hours on it a day and I am sure Alfred would be called at least double as much.