I have played around with a lot of Twitter applications for the iPhone. My least favorite one is Twitter’s official iPhone app and up until recently Osfoora was my favorite. However, Tapbot’s Tweetbot is now my favorite Twitter application for the iPhone, and I believe it is the best one.
The interface is very slick and they actually created a joyful experience using sound effects to enhance the experience vs. ruining it. If you do not like it, you can mute it. However, Tweetbot has a few features that I have not seen done well in other iPhone applications:
Muting
One of the best features on Tweetbot is the mute feature. Do you ever have times when you want to mute someone you’re following because they are in a Twitter chat, watching a show or sport, or (like me sometimes) just tweets too much? Rather than unfollowing, Tweetbot has a mute feature, which you can actually set the duration you would like to mute them. Keep in mind that this only works on the iPhone app itself and you will see those tweeps in your timeline if you view on another app or the web. It is actually a feature that Twitter should implement themself.
Note: I actually did not mute Guy. This is just a screenshot ;)

Lists As Your Timeline
This is probably my favorite feature. I can browse my timeline as different lists I have. If I am not in the mood to read all tweets from the 900 or so people I follow, I can simply select a list. The nice thing is when you dismiss the app, it will default back to that list you selected.

Drafts
Like the Wren app for the Mac, Tweetbot allows you to draft up tweets versus just posting like crazy. As I use Twitter more, I realize that I do not want to just shoot off thoughts out of the blue, but instead prefer to keep it on ice for a bit. The drafts allow you to queue them up.

Notes
Who are we kidding..this is an identical copy of notes for the iPhone. However, it’s great because it’s in app. I use this feature to write responses and jot down ideas of things I want to tweet about later.

Tweetbot overall is worth the few bucks to use or at least try out. I really rely on Tweetbot when I want a lighter viewing experience on Twitter. Sometimes my timeline is a bit overwhelming and I use Tweetbot for a more intimate experience.
You can download it on the app store here.