don't forget OS/400 and it's precursor System 32-34-36-38 that ran on IBM mid range systems.
Then on PCs and mid range was PICK.
On PCs there were all the flavours of Novell's Netware including Advanced Netware, Netware 3/4/5/6
And for the really obscure there is Y2000 an IBM S/360 mainframe operating system developed by Philips Electronics and used internally in the 1980's.
I'm off to get a life....;-)
How Many Operating Systems Can You Name?