I feel like we have to exclude any OSU win or the App State game - those are gimmes.
Off the cuff, I'll go with their 2001 loss at Michigan State (the game with the Sparty timekeeper that held an extra 0:01 on the clock allowing MSU to score on the final play of the game). That seemed to produce some tears and, coupled with our 2001 win up there, kept them out of a BCS bowl. Other candidates from that era, when Michigan losing actually meant something:
- Their nutty 54-51 loss at Northwestern in 2000 when Anthony Thomas fumbled while running out the clock
- Their 2002 home loss to Iowa where they got absolutely dismantled, 34-9.