1) Format For Post
The different types of Post Format have been changed in WordPress 3.6.
2) Browse your auto saved revisions
From the Different auto saved post, we can browse any and have it auto return when required by just browsing it back.
3) Attached Files
We can what all image are being attached to the post, which is a feature differ from featured image.
4) Media Filter
Previously it was just about images, now we have different filter for all type of files attached. For e.g PDF below.
5) Post Locking
Post locking have been in Joomla, now its been added to WordPress too, It notifies multi editor for post that are under changes by other editor.
6) WordPress 2013 Theme
From all the themes of WordPress, we can now use WordPress Theme “Thirteen” as our new child theme, which have a brand new look and support for new features.