just adding my 2 cents for what the other have mentioned already.
To OSX/Linux/Windows I install:
Libre Office (I haven't seen compatibility problems with MS office for years, but I'm cautious when opening MS files)
VLC
Gimp
7zip
firefox
winamp
and if it is windows machine, Avast antivirus, ccleaner and auslogic disk defrag, but the last 2 mostly to clean up after the primary installations, I don't expect their users ever bother with them till they call me because their PC is slow
also does steam and spotify qualify for this list?
add them too