"Chicken of the VNC", or CoTVNC, is simply a VNC Viewer for MacOS X. 
It includes speed optimizations, customizeable CPU throttling for the
frontmost and other connections, a manual Refresh command, and 
Tight encoding. It's a good compliment to OSXvnc, a MacOS X 
VNC Server.

It's open-source and MacOS-X only. You can get a copy here:

http://sourceforge.net/projects/cotvnc/