The Pittsburgh Pirates have done a great job of signing their draft picks this year, getting 33 of the 41 picks into the organization already. Of the remaining eight, there aren't many options that could be a possibility as the 5 PM deadline approaches today. You can view the draft signing tracker here.
I'll note that the tracker notes that the Pirates have up to $399,418 available for over-slot picks before they face a penalty that includes losing draft picks. Right now they are in the 0-5% range over because both Ike Schlabach and James Marvel required over-slot deals, though neither figure has been announced.