A version of Windows NT Server which actually allows multiple users to log on to and run applications on a single server, developed only thirty or so years after Multics, ITS, and GECOS (among others) got timesharing right the first time. Also known as Hydra, though unlike its mythological counterpart, cutting a head or two off unexpectedly will tend to kill it messily.
It's actually great in principle, as anything that can run the thin client can run W32 apps off of a server. A popular demo at trade shows is to show off a 286 motherboard hooked to a monitor, mouse, keyboard, and single floppy drive (and nothing else, no hard drive) which is using the client to run Office 2000. But since W32 is such a resource hog, it takes a lot of server to service more than a handful of users. The hardware required to support 25 people running single apps (never mind full desktops) on NT Terminal Server would easily accomodate 100+ if a Real Operating System were in use.