STORMWATCH  mFurc is a pretty good port of "Furcadia". It lacks some important features (mainly, character creation, so you must have created one with the Windows client first). But since it was done without access to the source, it's still quite a feat. Kudos to the developer.

The only thing that annoys me is that support for G3 was recently removed. Why? How come my old iMac can run "Quake III" just fine, but not something much older and simpler?  
(Version 2.04)