If you are an avid Twitter user and addicted to use it from your phone. Then you should try Gravity. Its Symbian S60 based Twitter client. Which has very cool and usable interface. I have also tried Snaptu and TweetS60, which are free. But Gravity gave me great experience. I am using it on my Nokia 5320 Xpress Music.
You can download Gravity v1.2 from here.