Even if you consider Borat (full title not necessary) to be primarily a scripted work, it is still a film that works best in its unscripted sequences. This is debatable, sure, but I would like someone at the Writers Guild to tell me what was so great about the actual screenplay used. Personally, I think the scripted parts, as well as the adherence to the plot, are the weakest elements.
Nonetheless, Sacha Baron Cohen and his five collaborators are nominated for a Writers Guild Award for Adapted Screenplay. And despite my questioning of this recognition, I don't really prefer any of its competition. The other titles in the adapted category are Little Children, The Departed, The Devil Wears Prada and Thank You for Smoking. If I had to choose, I'd go with the last of these, but I think the prize will go to the overrated Little Children.
I also don't think the Original Screenplay category is that great, either. The nominees for that award are Little Miss Sunshine, Babel, United 93, Stranger Than Fiction and The Queen. Again, I'd have to go with the last of these, but predict the overrated first.