Marcus Rush.
He was undersized, and early in his career was nearly useless in short yardage situations. I think in the 2011 Wisconsin regular season game, MSU had to take Rush out, because UW was just running at him every play. But he was a 4 time HM All-Big Ten player, who had the fortune/misfortune of playing opposite Will Gholston and then Shilique Calhoun, possibly the two best DE during that time. That meant he was never going to be the guy opponents worried about, but it also probably jaded my opinion of what a good DE should be.