With all of the changes happening over at Twitter yesterday, John Gruber posted a great analysis on Daring Fireball. I too, was a big fan of Tweetie, an independent app created by Loren Brichter under the company name Atebits. Tweetie won the Apple Design Award in 2009 and was also the debut of the pull-down-to-refresh functionality that is so popular in iOS apps now. Loren was hired by Twitter in 2010 and Tweetie was rebranded and became the official Twitter app on the iPhone. With all of the "dickbar" stuff that happened since the acquisition, I switched to another app, but I still think that the original Tweetie was amazing.
Also, here is a great History of Tweetie created by Jeremy Stanley