The Twitter app is the official mobile offering for the microblogging service. While it used to lag behind third-party Twitter apps, it's now arguably the best way to tweet and engage with your followers.
Twitter's official iPhone app
Free social application for Android
Broadcast your life
Slick client by the makers of Twitter
Save on data when you tweet
Twitter app for Windows
The best desktop Twitter app
Stay up-to-date and informed on Twitter
Mobile Twitter on the big screen
Official Twitter client for Mac
Use Twitter With Precision, Power And An All-In-One View.