Pimp your GNOME Desktop
The real title of this post should have been Pimp your Metacity, but not everyone knows that Metacity is the official window manager of GNOME.
This is just a modified version of the default theme in Ubuntu Karmic Koala. The main difference is that the minimize, maximize and close window bottons has been removed. They are only activated by mouseover.
It is useful for users who already know the position of the window buttons in GNOME and all the time use keyboard shortcuts to manage the windows. And especially useful on small screens like netbooks where there is not enough space avaliable to display redundant things.
The Human Simple theme can be downloaded from GNOME-Look http://gnome-look.org/content/show.php?content=118052