Ahem; JTwitter is actively maintained, regularly updated (version 1.6.2 released today), and covers most of the Twitter API.
It's missing only a method for setting your profile image and a few other profile settings. Other than that, it's pretty complete. Status updates, timelines, friendships, lists, searches, streaming, etc.
It's also fast and robust. Twitter can be flaky in places and JTwitter has work-arounds and informative exceptions to make your life easier.
As the main JTwitter developer, I am rather biased! But the feedback from developers using JTwitter is also very positive.
