Von Unsanity gab es mal Shadowkiller...
Hier ein Thread zu anderen Möglichkeiten.
http://www.reddit.com/r/osx/comments/2lyg3u/is_it_possible_to_reduce_or_remove_the_window/
http://www.reddit.com/r/osx/comments/2lyg3u/is_it_possible_to_reduce_or_remove_the_window/