NetWare - it used to be the only option for a file and print server if you had x86 hardware. Even when NT became available, people would scorn it in favour of NetWare's superiority.
Nowadays, things are a bit different. It's still superior in most large enterprise respects - it is stable, well documented, easy to manage, and scales like a trooper! Hardware support is dying off a bit though, and migration to those lovely "lock-in" applications like MS-SQL and MS-Exchange, coupled with the rise of Linux as a file and print server, is slowly squeezing NetWare out of the market it helped to create.
NetWare 6 though, it must be said, is LOVELY!
Stuff it can do (aka features):