Most of the time I use the "hold alt + drag middle mouse button in a direction" to rotate the view. There are often times when I want to see the top or bottom view and then rotate the top/bottom view by 180 degrees along the Z axis.
I know I can rotate the view 180 degrees by pressing the Numpad_4 or Numpad_6 keys twelve times but I rather have a shortcut I can press once or ideally, a way to do it with the middle mouse drag gestures since using the numpad is a bit cumbersome when my right hand mostly sits on the mouse.
4
,9
,6
on the Numpad from top/bottom view. Its a bit of a hack but it works. It takes you off orthographic mode, though. $\endgroup$