Google Chrome - When dragging the active tab it is always on top of the others, when dragging an inactive tab it moves behind the active one.
/via Blake Simpson
Amazon - After completing your order, the page title changes to: “Amazon.com Thanks You”
/via Steven Scarborough
Sublime Text 2 - When two or more files of the same name are open, the folder path is appended to the tabs.
Asana - Holding the tab button underlines the first letter of each possible detail to indicate the keyboard shortcuts.
/via Nassar Hayat
Firefox - If you start typing a URL and you already have a tab open of that URL, the first option in the dropdown offers to switch you to that tab.
Flickr — When uploading files, it shows percentage in the tab, so you can always see the load progress while surfing other sites.
StackOverflow - When clicking a tab in the help bar, the matching icon on top of it start jumping up and down.
/video - http://d.pr/wtEd