In my time paying close attention to the Sox I would say:
Jon Rauch and Joe Borchard
I also vaguely remember a few guys from the mid-late 90s:
Mike Caruso, Brian Simmons, and Scott Ruffcorn
I don't think you can call Parque, Baldwin, Wells, Cameron etc. all "busts" because they have/will/did contribute at the major league level for some period of time for us and/or other teams. In the crapshoot that is minor-league prospects, I think if you get more than a full season of serviceable to decent production from a guy then you can't call him a bust.