Babacar. He's behind in the pecking order at Fiorentina, and could probably get a good deal for him.
Also still think Sandro has something to offer, he just needs to play. DCL has been good at running and harassing defenders, but rarely looks like scoring and Niasse is a decent enough option off the bench but again, he's a bit shite. But both have been given the opportunity. I'd like to see Sandro get the same.