UberSocial for Twitter is a client for the popular social network, and has a handful of very special features with which you can, among other things, create special circles for your best friends.
Thanks to this feature, possibly the most interesting of the lot, you can have a sort of 'favourite users' among the people you follow. This allows you to be even more aware of any tweets, which is particularly useful for anyone who follows more than two hundred people (many do, by the way).
In the same vein there is another feature that, while a little more common, is equally useful: silencing. This lets you stop reading a user´s tweets without having to stop following them.
The other benefits are somewhat more run of the mill: the possibility to manage multiple accounts from the same application, closer monitoring of conversations, or different options for uploading photos.
UberSocial for Twitter is a very comprehensive client that offers enough features and customization options to satisfy even the most demanding users.