Comment by gks

Apps that I install immediately upon re-installation or a new Mac:

* 1Password - Password facilitator (http://www.agilebits.com, buy the Mac App Store version)

* OmniFocus - GTD/Todo list (http://www.omnigroup.com/omnifocus)

* OmniOutliner - Best list makinga pp ever (http://www.omnigroup.com/omnioutliner)

* OmniGraffle - Great for development purposes (http://www.omnigroup.com/omnigraffle)

* Acorn - Quick image editing (http://www.flyingmeat.com/acorn)

* VoodooPad - Personal Wiki (http://www.flyingmeat.com/voodoopad)

* Byword - Markdown editor (http://bywordapp.com/)

* Dropbox - Duh (http://www.dropbox.com)

* Fantastical - Calendar app (http://flexibits.com/)

* Launchbar - Launcher (http://www.obdev.at/products/launchbar/)

* Reeder - Google Reader client (http://reederapp.com/)

* Transmit - SFTP (http://panic.com/transmit/)

* VLC - Video (http://www.videolan.org)

Along with iA Writer, Writeroom, Sublime Text, etc etc... there are a lot of great apps. The above is my favorites.