Gnome-Pro, a new GTK+ theme made by paulxfce, is a great theme for Gnome 3 Desktop with GTK > = 3.20.
A clear and easy-on-the-eyes theme that is meant for those who use the Gnome-desktop professionally on a daily basis. The focus in this theme is compatibility: GTK-2 applications and GTK-3 applications look virtually the same. Libre-office, Scribus, Evolution, Geary, Planner, GnuCash, LaTeXila, Geany, the Gimp, Inkscape,…
Chrome, firefox, Web and Opera have no issues with this theme.
About the looks, you will notice some Elementary-theme, Arc-theme and Gnome-OSX.