Gottfried Hofmann walks you through the knife and bisect tools and their various options in this tutorial for Blender 2.83 or later.
With the annotate tool in Blender 2.8 you can draw anywhere in 3D space or directly onto the "screen" of the 3D view.
In Blender 2.8 the camera got viewport widgets as well. One to change the focal length which is always on and one to change the focal plane which needs to be activated first. Gottfried Hofmann gives a quick overview.
Learn more aboute the inset tool and its various options in Blender 2.8 in this new overview video.
Blender 2.8 comes with a new tool- the measure widget. It allows you to measure distances, angles and even the wall thickness of 3D objects.
In Blender 2.8 light objects in the viewport have widgets that allow for a point-and-shoot lighting workflow, easy resizing and more. Gottfried Hofmann guides you through all of them.
This tutorial by Gottfried Hofmann shows you the extrude tools and widgets in Blender 2.8.
The loop cut tool in Blender allows you to place cuts that follow the topology of our model and the offset edge loop cut tool even works in two directions at once.