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JollyFastVNC is the best VNC client you'll ever find. It's not exactly free, but you can keep clicking the "Try" button. I highly suggest paying for it because it is that good.
 
Chicken of the VNC works quite well, and is actually free, too. I've used it for a long time.

You also have a built-in Screen Sharing app that can be made to work with any VNC server. Just put in the address of the server in Safari in the vnc:// format, and the app will open.

jW
 
I used Chicken of the VNC in the past, and liked it. Now I tend to use the built-in Screen Sharing application, which is located in /System/Library/CoreServices.
 
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