Alt Tab Mod: Only Raise Activated Window
GNOME Shell extension. Supports GNOME Shell 3.6.
When you Alt+Tab to an app (instead of Alt+ to a window), default behavior is to bring up all windows of the selected app and activate the most recently used. This extension modifies Alt+Tab to always bring up only the activated window.
OBS: not guaranteed to work together with other extensions that also modify Alt Tab popup. Tested only with 'Alt Tab Workspace'  and other 'Alt Tab Mod: ...'.