Executive for GNOME Shell is a new theme pack that comes with 2 GTK themes (grey and green), a GNOME Shell theme and two icon themes.
Currently there aren't many matching GNOME Shell / Metacity / GTK2/3 themes, so Hhhorb, the Executive pack author, has modified some already existing themes to do just that. And the result is great:
The beautiful GNOME Shell theme you can see in the screenshots above is Gaia Shine - notice how the Metacity theme looks exactly the same as the top GNOME Shell bar. The GTK themes look great too and I especially like Executive Green, however, I'm not of fan of the included icon themes (you can see one of them - Executive Brave - in the second screenshot) but you can always use elementary, Humanity, Faenza / Faience or Awoken icon themes instead.
To use it: download Executive for GNOME Shell via DeviantArt, extract it and copy the Executive, Executive-green and Executive-blue folders in the ~/.themes directory (if it doesn't exist, create it). If you also want to install the icons, copy the gnome-executive and gnome-brave folders under ~/.icons (once again, if the folder doesn't exist, create it).
Once you copy the folders, use GNOME Tweak Tool to change the theme. Please note that you'll need GNOME Shell User Themes extension to be able to change the GNOME Shell theme. Also, after changing the Metacity (Window) theme, you'll have to reload GNOME Shell to apply the changes - to do this, press ALT + F2 and enter "r" or log out and log back in.
Thanks to Hhhorb for the tip!