Felix Geisendörfer's (@felixge) faves, and what he said about them in his tweets of 07 April 2011:
I really wonder how I was able to use Terminal app all this time. iTerm2 is so much better, it hurts. (#)
If you find yourself arranging windows with your mouse on osx, give it a try. #cantlivewithoutit (#)
Makes searching code incredibly fun & easy. I often use it via ack.vim to jump around in projects as well. (#)
Like TextMate's fuzzy file selector, just more awesome. Matches paths, integrates with git & most editors. (#)
Reliably predicting fan noise since '2003 (#)
Best little timer app for osx. Helps me time boxing things every day. (#)
Saves me from the sins of procrastination. (#)
Keeps my download folders and desktop tidy. (#)
My app launcher since quicksilver became abandonware. I only use a fraction of it's powers so. (#)
(Bill's addendum: Yay, a Viennese company!)
Makes gmail kick ass on osx. Supports multiple accounts. #cantlivewithoutit (#)
Awesome osx client for campfire. @transloadit would not be a success without it. (#)