David Montgomery, RB
It's 2024, so it's not like the Bears were about to pay Montgomery huge money. He was a good-but-not-great running back during his four years in Chicago, and deserves a ton of credit for being one of the few decent players on some rough Bears offenses. He'll always be associated with that terribl(y funny) TV graphic meme, but it's impossible to say he wasn't productive for them: in four years, Montgomery put up 3609 rushing yards and 26 touchdowns in 60 games (51 starts). There were more than a few moments when he had Soldier Field on their feet after 3-4 broken tackles. (And yeah maybe they all happened behind the line of scrimmage, but whatever.)
They let him walk after 2022, and he didn't go far, signing with NFC North rival Detroit on a three-year, $18 million deal. He was a major part of Detroit's offense in Year 1 – and playing behind that offensive line didn't hurt – going for over 1,000 rushing yards for only the second time in his career and scoring a career-high 13 touchdowns. And there's probably an argument to be made that the Bears have been fine with Khalil Herbert and Roschon Johnson, but neither have been close to as good as Montgomery was on his own last year.