From the docs:
DOM Property Viewer
Inspect the page's DOM properties, functions, etc.
(You'll notice properties of the object are not usually listed in console in Chrome, you would never know that body.innerHTML existed, looking at "document.body" in the console.)
Developer Toolbar
A command-line interface for the developer tools.
Shader Editor
View and edit the vertex and fragment shaders used by WebGL.
Web Audio Editor
Examine the graph of audio nodes in an audio context, and modify their parameters.
Taking screenshots
Take a screenshot of the entire page or of a single element.
Some extra tools in the settings panel:
The network panel shows the stack trace of the cause of each network request, in Chrome you have to go through console log of network requests and find the one and expand it. Also, you can see the actual preview (in preview tab) of a xhr response if it happens to be html returned.
And perhaps the most useful, the inspector shows (ev) beside every element with an event listener on it, with direct listing of everything that adds event listener to it. (nicer than Chrome's event tab listing to the right.)