The "File" menu currently uses a non-standard icon for "save" that is not used by another other application, and is therefore unrecognizable and unsuitable for such a use.
All of the current members of the UI team strongly favor a change from the current icon, and almost every single user preferred using a traditional "floppy" icon for this purpose. I can only think of one user that liked the current non-standard one. This patch replaces the current icon, created by Andrzej Ambroz (jendrzych) and replaces it by another one also created by the same artist.
The following compares what the save icon looks like now (on the left) with what it looks like after this patch (on the right):
This patch contains the changes to the SVG source file for all the icons: "blender_icons.svg". But to see this change (without needing to run "blender_icons_update.py"), you also must replace two icon "dat" files as well. The following zip file contains "icon16_file_tick.dat" for the "blender_icons16" folder, and "icon32_file_tick.dat" for "blender_icons32" folder, each in /release/datafiles.