Tweetbot - Sync your timeline across your iPhone, iPad, and Mac. Mute tweets by user, hashtag, tweet source, or keywords (including regex). 3rd Party support for image, video, read later, and timeline sync services.
YoruFukurou - YoruFukurou (NightOwl) is a Twitter client for Mac OS X, designed for Twitter addicts.
Twitterrific - Twitterific is an app that offers several functions and fun features for your Twitter account.
Janetter - Janetter is a Twitter client application. Faster, smarter, and more powerful.
X (Twitter) - Connect with your friends and other fascinating people. Get in-the-moment updates on the things that interest you. And watch events unfold, in real time, from every angle.
Talon for Twitter - Elegantly designed, ad-free Twitter experience for Android