In 2006, the third seeded (in the Minneapolis bracket) University of Florida gators defeated the #2 seeded UCLA (in the Oakland bracket) in the national championship. Neither team was a number one seeed
Michigan was a #3 seed when they won the NCAA Men's Basketball Tournament in 1989.
16 seed, beat duke last year
Villanova (#8) in 1985
8 seeded Vilanova in 1985
8th, the lowest seed to win it all
Kansas was the #6 seed in the Midwest bracket in 1988.
8 Villanova over Georgetown
#1 seeded Kansas defeated Kentucky in the second round of the 2007 NCAA Tournament, by a score of 88-76.
16 seeded Harvard defeated 1 seed Stanford in the 1998 women's NCAA tournament. That is the only victory by a 16 seed in either the men's or women's tournament.
Michigan State Vs Louisville in the 2012 mens NCAA tournament. Michigan State scored only 44 points as the lower seed Louisville Cardinals ousted the number 1 seeded Spartans.