No Guest User
The Guest User has disappeared from my user drop-down and from the Login Window despite being listed in the "Users & Groups" pane:
iMac Line (2012 and Later)
Question marked as
I tried turning off "Allow guests to log in ..." (see above) and then turning it back on again. And, to my surprise, the "Guest User" option has re-appeared in both the user drop-down and the Login Window!