TU plugin uses 1 instead of a real user capability when adds its menu item to the “Settings” menu (twitter_ultimate.php:15):

add_options_page ( "Twitter Ultimate", "Twitter Ultimate", 1, "twitterultimate", "twitterultimate_settings" );

I can just suppose that this plugin is quite older and uses the deprecated user level 1.

So this menu item is available to any user with the deprecated ‘level_1’ capability.

Solution 1st: edit ‘twitter_ultimate.php’ file and replace 1 with ‘manage_options’ or other user capability on your choice.

Another solution – revoke level_1 deprecated capability from a role for which you wish to prohibit access to this menu item. User with such role can disappear from the list of authors at the post editor page though (more information).