OSX Nostalgie: http://gnome-look.org/content/show.php/OSX-Nostalgie?content=157390. This icon theme is a copy of the default icon theme for Macintosh OSX.
Faenza: http://gnome-look.org/content/show.php/Faenza?content=128143. This is the highest rated icon theme on the Gnome Look website.
Win2-7: http://gnome-look.org/content/show.php/Win2-7+Pack?content=113264. The Windows 7 transformation pack for Gnome. This will make your Linux desktop look like Windows 7.
Elementary icons: http://gnome-look.org/content/show.php/elementary+Icons?content=73439. A beautiful icon theme for Linux Gnome desktops.
Ubuntu style: http://gnome-look.org/content/show.php/Ubuntu+Style?content=157153. A lovely icon set for any Ubuntu desktop.
Clarity: http://gnome-look.org/content/show.php/Clarity?content=135654. A lovely vector icon theme for Linux desktops.
Glass: http://gnome-look.org/content/show.php/Glass?content=159358. This an interesting glass icon theme for Gnome.
Nitrux OS icons: http://gnome-look.org/content/show.php/Nitrux+OS+Icons?content=154496. A lovely icon theme for Gnome. This one is stunning.