Keith Law's new MLB mock draft (it's insider-only, but you can check out a synopsis at MLB Trade Rumors) has the Pirates taking Virginia pitcher Danny Hultzen at No. 1 overall.
This would be very surprising to me. College pitchers have a reputation for being "safe" picks, but the track record of college pitchers selected at the beginning of the first round has actually been horrible, and the Pirates, who were burned by Bryan Bullington as the first overall pick in the 2002 draft, should know that as well as anyone. If they are going to take a college pitcher, I would think UCLA's Gerrit Cole would be more likely, but Cole's stock has slipped in recent weeks.
That leaves Rice third baseman Anthony Rendon and a few other less likely picks, like high school pitcher Dylan Bundy. Assuming Rendon checks out medically (and he might not), I would go with him.
The closer we get to the draft, the less certain things look for the Pirates. That's not good - it would be far better to have an Alex Rodriguez or Ken Griffey Jr. or Stephen Strasburg or Bryce Harper kind of situation where there's an obvious No. 1 pick.