I recently went searching for a VNC client/viewer for Mac OS and stumbled upon an interesting fact. Since version 10.4 of Mac OS it has come with the Screen Sharing package which is essentially a VNC client.
The easiest way to access the VNC client is using the Safari browser by specifying vnc as the protocol and the server name or ip address as the destination. eg. to access the server 10.0.0.50 use this url vnc://10.0.0.50