Sal -> Gun Lust. The only skills that appeal to me from that side are Divergent Likeness and Money Shot. At least in my opinion, Sal is better off with a focus in Rampage (Gunzerk forever.) and left-over skills in Brawn.
Zero's damage bonuses from sniping are quite ridiculous...not sure how anyone could *not* like that unless they don't like sniping in the first place. I think he's better off with that at first, then flip it around late-game to a focus on Cunning with left-overs in Sniping. Bloodshed tree is the one that isn't really all that aside from "Execute", imo.