I would probably also run OS 9 on it. I had Tiger running on one briefly, and it was terrible. It was only usable to open an app and print, and it was used at the time as a cheap method to control prints to a very expensive printer.

Panther or Jaguar might be nice, and if you kept it offline, that early version of OS X would be a neat oddity, but in terms of actually doing stuff with it, I'd just wipe the drive and put OS 9 on it.

Did you get the install media with it? If not, you may consider (if it's reasonable)_ replacing the hard disk, for 1) performance 2) so you can preserve the original configuration, easily.