Many come to mind..to narrow it down to one??? Impossible...
Game of the Century (at the time in NCAA Football) - 1971 Nebraska over Oklahoma
NCAA Hoops - Duke over Kentucky - Lattner shot at buzzer
Boxing - Douglas over Tyson
Personal favorite - Nebraska over Miami (Warren Sapp and Ray Lewis) in 1994 for Ozzy's first national title..I was there...cried my eyes out..
NFL - Broadway Joe and the Jets over the Johnny U and the Colts.... (Think that was 1970) ?
Mark Spitz - 7th Gold medal in 1 year in Olympics
Golf - Nicklas at Masters when he was 46 years old - followed closely by Tiger winning US Open at Pebble Beach by 11 strokes
Team USA in Hockey in Olympics...1980 I think???
Just a few that jump out...