Twittelator is a fantastic twitter client which intially was for the iPad and has since moved on to the iPhone as well. Twittelator on the iPhone Provides a variety of functions which other clients do not provide. It has an extremely user friendly interface, it is a very customizable client. However at $4.99 in the app store this application is a bit over priced. Nevertheless it is a great twitter client and I would definitely recommend you get it.
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