In one of the more infamous trades in sports history, in 1964 the Cubs sent Lou Brock, along with two other players, to the St. Louis Cardinals for Ernie Broglio, Doug Clemens, and Bobby Shantz.
Broglio pitched 213.1 innings for the Cubs, amassing 102K, 114 BB, and allowing 33 HR.
Doug Clemens spent just over a season in Chicago, hitting .238/.319/.327 (admittedly slightly better than his career .229/.317/.321) before being traded for Wes Covington. Covington would get 12 PA where he managed 1 H, 1 B, and 2 K before being released.
Bobby Shantz pitched 11 innings for the Cubs, striking out 12, walking 6, and allowing 2 HR, before he was purchased by the Phillies.
Lou Brock went on to have a Hall of Fame career for the Cardinals.