Rank as many as you'd like:
1995 Notre Dame (45-26 win at The Horseshoe in 1st meeting since the 1930s)
1996 Notre Dame (29-16 win in a top 5 matchup in South Bend)
1997 Arizona State (20-17 Rose Bowl comeback win over the undefeated Sun Devils)
1998 Michigan (31-16 win to end 3 year's of futility)
2002 Penn State (13-7 win on Gamble's pick-6)
2002 Purdue (10-6 'Holy Buckeye!')
2002 Michigan (14-9 to clinch the Fiesta Bowl)
2003 Miami (Fiesta Bowl/NCG 2OT 31-24 win)
2005 Michigan (25-21 4th quarter comeback in Ann Arbor)
2006 Notre Dame (34-20 Fiesta Bowl win)
2006 Texas (24-7 1 vs 2 win in Austin, TX)
2006 Michigan (42-39 1 vs 2 Game of the Century)
2010 Oregon (26-21 Rose Bowl win for Tressel)
2011 Arkansas (31-26 Sugar Bowl win, getting the SEC monkey off our back)
2012 Michigan (26-21 win to go 12-0 in Urban's first rendition of The Game)
2014 Wisconsin (59-0 Big Ten CCG perfection to make the CFP)
2015 Alabama (85 yards through the heart of the South Sugar Bowl/CFP 42-35)
2015 Oregon (CFP NCG 42-20)
2016 Oklahoma (45-24 win in Norman, OK)
2016 Michigan (2OT 30-27 win in 2 vs 3 game)
2017 Penn State (39-38 comeback in the Horseshoe)
2018 Penn State (27-26 comeback in front of the 'White Out' )
2018 Michigan (62-39 route, derailing TTUN's season)
2019 Washington (Rose Bowl win in Urban's final game)
2019 Michigan (56-27 route in Ann Arbor in Day's first version of The Game)
2021 Clemson (sweet Sugar Bowl vengeance)
Feel free to add others in the mix - I know I've left out some solid wins vs PSU in the 90s, Tress's guarantee in 2001, 2014's wins at PSU and MSU, the 2015 beat-downs of TTUN and ND, beating USC, and others - we've been pretty spoiled with great wins these last 3 decades!