I like a couple of guys out of Rutgers, RB Isiah Pacheco and WR Bo Melton.
Why are they late rounders/UDFAs? They went to Rutgers, weren't 5 star players out of HS, and never put up eye popping numbers.
Why do they have late round value? Shown to have NFL athleticism, have played against top competition, and have played special teams.
These guys aren't show ponies that will balk when they're asked to do the dirty work. They have had a chip on their shoulder since forever. Had they played with players found at Ohio State, Clemson, and Georgia, their names might be known. It's hard to put up big numbers behind a line that can't open up holes or a QB that can't hit the broad side of a barn.
These guys played 4 years (in Melton's case 5), never transferred, and did whatever was asked of them. They have the physical ability and attitude to you're looking for when filling out the back end of a roster.