Use Shift+Ctrl+Left click to select the faces or edges of polysurfaces. (You can then use the gumball to move/scale/rotate the selection)
Drag the gumball arrow in a direction with something selected, hold ctrl down then let go of the arrow. This will extrude rather than move.
Alt+drag gumball arrow to make a copy.
Shift+drag gumball scale box to scale in all directions.
Many people seem to overlook the shell command which let’s you quickly thicken some geometry.
Scrolling the middle mouse button when the mouse is over the viewport names at the bottom of Rhino will let you quickly switch between viewports.
SelectionFilter command is my favorite dockable menu which let’s you omit whatever geometry types you want from being selected (I personally think it should be out and docked in Rhino by default, many don’t know about it)
_MergeSrf command to join surfaces together without making a polysurface (makes a new single surface, even if surfaces are not co-planar)
MergeAllFaces command to turn coplanar polysurface faces into one face.
-ScreenCaptureToFile command for taking high res screenshots.
The cool morph commands like FlowAlongSurface, Sporph, Splop.
You can use FlowAlongSurface on control points and cage edit points too.