TweetDeck - TweetDeck is your personal browser for staying in touch with what’s happening now.
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.
Socialite - History Ever since we acquired Socialite from Realmac Software in December 2010, we have been planning on releasing a faster, more stable version 2.
Twidere - Tired of seeing ads and promotions in your timeline, being disrupted by tweets from bots and people...
Earthquake - Terminal-based Twitter Client with Streaming API support. Only supports Ruby 1.9 and later.
YoruFukurou - YoruFukurou (NightOwl) is a Twitter client for Mac OS X, designed for Twitter addicts.