Combination of features:
Look at the other twitter tools. Few of these have only follow and unfollow features, others have only post schedule management feature. But ManageFlitter has features like followers and unfollowers management, posts management, analytics and search for account or tweet.
Using ManageFlitter tool, you can manage your followers. You can follow people by keyword search, account search and tweet search.
You can also unfollow people from your ManageFlitter dashboard. You can unfollow people who are not following you back, who do not have profile image, who are inactive and also mark and unfollow the accounts look like fake/spam.