The CTH-CS exit off I-39/90/94 near Poynette was seldom used until the new Love's Travel Stop came along. Now there's a dozen semis getting on and off the Interstate there every two minutes.
MN 101 at CSAH 37 in Otsego. Same deal, except it was a Kwik Trip that got put in (over objections from nearby subdivisions).
NJTP Exit 16W. Not much there before they built the Meadowlands Sports Complex.
In CT, I-84 Exit 62 (formerly I-86/CT 15 Exit 93). was pretty much just for the old JC Penney warehouse before they developed the area starting with Buckland Hills Mall.