I know all too well we've lost the last three games to these guys but in my lifetime there were three nut-crunching losses to MSU that are stuck in my memory like the first fat chick you hooked up in the dorms when you were too drunk to notice but not drunk enough to forget what she looked like (more on that some other time).
1978 - MSU 24 - Michigan 15
The only conference loss for one of Bo's truly great teams. Senior QB Ricky Leach's only loss to MSU derailed Blue's march to a possible National Championship season as Kirk Gibson goes off (yes he played football too) and almost single-handedly defeats Michigan. The term "Arrogant Asses" is born.
1990 - MSU 28 - Michigan 27
#1 ranked Michigan makes a furious comeback and has a chance to steal the win (MSU outplayed us that day by a LOT) only to have the game end on the mother of all controversial "no calls" in college football history. Little known fact - the ref who ate his flag that day in the end zone was the high school coach the year before of the MSU defender who DIDN'T interfere with Desmond on the two point conversation attempt.
2001 - MSU 26 - Michigan 24
Spartan Bob....multiple drive extending defensive penalties against Michigan and.another insanely obvious no-call on the last play of the game leads MSU to two point victory that literally changed the rules of college football.
And besides the obvious answer "all of them" which one is yours?