There are some OS X clients that aren't listed on the download pages here:
 
- Acquisition, 
http://www.xlife.org/aquisition.php . It uses the LimeWire code as a backend, but has a radically different (non-Java) front end so it actually behaves like a normal OS X application. 
- There's a LimeWire clone called AquaLime 
http://www.geocities.com/mamiya0taru.../aqualime.html . I don't really know if that counts as a separate client though. 
- Several of the programs listed as "Linux" clients have Mac OS X ports, through the Fink project (GNU-Darwin and OSXGNU may also have ported them, I wouldn't know). Right now, gtk-gnutella, mutella and qtella are listed at 
http://fink.sourceforge.net/pdb/section.php/net . 
Please add some info about these to the Mac client list. At the very least Acquisition should be added--for the ported apps, perhaps a note and a pointer to Fink would be appropriate. 
Cheers,
vasi