The system I hand on heart miss the most though is Ultima Onlines' and not so much that the guild system itself was up to much (it was basically a tag on your name and a method of communication) but most guilds clobbered together and built a house of some description to act as their HQ.
Some of my fondest MMO memories are just sitting in my Guild Hall listening to the chatter of people organise dungeon trawls and crafting routines while playing a game of chess with someone. For such an old, graphically dated game there really isn't anything that offers immersion like that.
I am new to the linksheel stuff, but at least it does do the job of being able to chat with others in your linkshell. Though getting them there and removing if need to seem to be a problem, lol.
and for Kordain's post about UO, first lol and cool, we used ours as a base for where each group was going to go set up shop as highwaymen and bandits. I mean why mine my self, when I can just kill you and take your mining efforts. Edited, Oct 4th 2010 5:56pm by MeisterOtome