I woke up this morning and was quite disturbed to have a horrible blue cog with a yellow spanner in the middle as my Gmail favicon. From what I can tell the icon is the same icon used in the admin console but I've no idea what it's doing on my Gmail tabs. Anyway quick fix, in Gmail:
- Click the cog drop down and goto "Settings"
- Go to labs and search for "Unread"
- Enable the "Unread Message Icon"
Here's the horrible icon I described above.