OSeXy-Dark-Gtk2 is a GTK2 theme/style meant to go with the Humanoid-OSX-Black-ColouredButtons Metacity theme.
It, as the title states, much more OSeXy. It has rounded buttons and colors to match the aforementioned theme.
It is modified from the GTK2 Theme that is packaged with the "Space Green" metacity theme. An awesome wallpaper to go with it is "dirtlight".
Metacity theme used: