Lost my rotary selector (Tab Key Pie Menus) I just updated to v2.79 and found that the Tab key mode selector is gone. When the Tab key is pressed, a rotary selector appears that allows selection of any of the available modes. I had added it under v2.78c to make it easy to select different modes. I can't remember where I got it. I remember finding it in a video tutorial, but which one (I've favorite-ed about 200 so far).
The Pie Menu is an addon

You can enable/disable it on the User Preferences Add-On section (Ctrl+ Alt+U) 



Note that one can customize which Blender menus are displayed as pie menus using Preferences settings group in the User Preferences > Pie menu rollout (settings are available only after the addon is enabled):