"AquaScroll" Feature
Add the ability to change the focus to a window under the cursor without bringing it to the front allowing you to use the mouse wheel to scroll partially obscured applications in the background without clicking on them and bringing them to the front. You could call it AquaScroll.
This feature has already been implemented on certain Mac and Linux versions but has not been implemented with previous versions of windows until 10. Certain applications like Google Chrome (and the newer versions of Microsoft Office I am told) support this feature with other windows/tabs within the same application, but no cross-application scrolling is permitted.