There are a lot of Twitter clients for your Android phone available in the Android market, which does not make it easy to pick the client that best suits you.

I think it's impossible to pick a best Twitter application for Android, because different clients shine in different areas, but below you will find a selection of the leading clients, available in the Android market at this moment.

Twidroyd
Twidroyd, formerly known as Twidroid, is a famous and very popular Twitter app, available in the Android market in a free and Pro version.

Logo TwidroydBoth versions provide you with the Twitter functions you need, going from the basic functions like sending tweets and (un)following users to more advanced functionality like URL shortening and geotagging. The Pro version has an integrated buzz viewer, color themes, tweet outbox, native bit.ly support, desktop widgets and multi-account support, functionality that the free version does not have.
Twidroyd's user interface is attractive and simple, which is also one of the main reasons why the app is so popular.

Twidroyd's free version as well as the Pro version ($3.99) are available for download in the Android market.

Seesmic
Logo SeesmicSeesmic offers many power features, such as multi account support, remembering your scroll position and geotagging. Seesmic has a beautiful, yet simple interface with all the main features easy accessible.

Seesmic is free and can be downloaded from the Android market

Tweetcaster
Logo TweetcasterTweetcaster is another very popular Twitter app. This client has a very beautiful user interface, which attracts a lot of people to Tweetcaster. The application is feature-rich and can be easily be used by new Twitter users as well as power users.

Tweetcaster is available in a free version, but if you prefer an ad-free Twitter app, then you can download the Pro version in the Android market for $4.99.

Touiteur
Logo TouiteurTouiteur, the Twitter application with a French sound, is well-known in the Android-community for its beautiful design of the user interface. Navigation through the client is really easy by using the tabs at the bottom of your screen. The Pro version of Touiteur comes with multiple account support, customized themes and a widget.

Touiteur free and Pro ($1.99) are available for download in the Android market.