Buzz, a small amount of play is fairly common, and not a great concern. As for the "clank"...are you actually bottoming? My first suggestion would be to look for something maybe loose or moving, often other than the actual suspension. Often times a clank is not actually suspension related, just happens to appear with the particular "shock" of landing.
Make sure you have the right spring for your weight and that sag is set correctly (but I'm sure you've already covered these items).
Wizard, if you are seing an oil ring...you have a leaking seal head that should be replaced. A good indication is a ring of dirt on the dust cap (where the shaft first enters the shock). If the head is leaking, this may account for your clanking. You too should check your springs adn sag. If you are bottoming badly, this is a good place to start. Also try increasing compression a little at a time to help with the bottoming....but remember, if that seal is leaking, all the adjustments in the world will not cure it.