Tymir Oliver and Kenyon Jackson are both big-time contributors at defensive tackle for the Illini. They came from the class of 2016 and were both two-star recruits. Jake Hansen was also in that class and he has been a star for the program the last couple of seasons at linebacker. He was only a two-star as well.
You can go back even further and find lower rated recruits who exceeded expectations. Reggie Corbin was a two-star and is one of the best running backs we have seen in a long time. Tre Watson was a two-star and he was a great linebacker for the Illini.