My first polystone statue was the Rambo IV 1/6 by HCG, I just got the 1/4 Rambo IV statue and it's great, very heavy piece, fantastic attention to detail on this, great job by Edinho Maga. I also have the Rocky Sideshow bust, so I think that one may have been the first polystone for me.
First ever polystone statue was Bowens Sandman Arabian Nights. First SSC was Emma Frost Comiquette. First direct SSC purchase was Iron Spiderman Comiquette.
My first polystone purchase (and first from Sideshow) was the Thanos/Lady Death comiquette. I received one of the many damaged ones unfortunately, so I ended up returning it and getting a refund. Haven't purchased anything made of polystone since, but I'm sure that'll change once more of the DC pieces begin rolling out.