I'm gonna go with the three big guys who will all need time to develope.
Davis from Mich St. If he's there at 12, Ainge should trade up to get him.
Bender. He's no stiff. Can move and is extremely coordinated for his size. If he falls we should take him.
Lab from Kentucky. He probably will need a couple years to even crack the rotation but he has the potential to be one of the best in the draft. Huge risk but high reward.
All three picks are gambles that I would take.
Deyonta Davis intrigues the heck out of me. Noticed that he only now just cracked the lottery in DraftExpress' mock this week. But Mich St. has a logjam of seasoned bigs. The most recent article I can find about him comes from late January, and when compared to other top freshmen big prospects (Lab, Rabb, Stone, Zimmerman, Diello, Bryant), his adjusted stats (40 mins) were really good: third in points, third in rebounds, first in blocks, second in TS% and second in AST/TO ratio.
He needs time to develop, especially offensively. His shot doesn't look broken, though, and he has shown flashes in the post. Defensively, he looks like a very versatile rim protector that can stay with 3s on the perimeter. Needs to beef up quite a bit, but he may even still be growing at 19. Would expect his stock to increase a lot if he stayed another year. I would definitely take a chance on him if he's still around with the DAL pick but not sure that will happen.