Here's my new extension for Gnome 3: Right-click on Activities toggles that button to Applications. After that, either clicking on Applications or pushing the mouse into the hot corner brings up the Alt Tab options, which remain on screen until clicked with the mouse.
This extension allows the user to rapidly switch between applications without spending two or three seconds searching for an awkward key combination.
I think this extension is a useful addition to Gnome 3 functionality, perhaps even an indispensable one.
The only minor drawback is that I have no programming skills, so it's only a concept. Maybe somebody will read this and turn the specification into a real extension...
Update: Microsoft did... for Windows 10.
(The third icon from the left is Task View, which does exactly what my proposed extension would have done.)