Super Bowl XXVII, January 31, 1993; 1993 Thanksgiving game

What happened: Lett, the Cowboys' talented but troubled defensive lineman, could have his own top-10 list. In fact, on ESPN's 25 Biggest Sports Blunders, he occupies two of the top three spots. His premature celebration in Super Bowl XXVII is the gold standard. An oblivious Lett allowed Bills receiver Don Beebe to poke the ball out of his hands for a touchback as Lett rumbled toward the end zone. But what really sticks in the minds of Dallas sports fans is Lett's infamous Thanksgiving game performance the next year against the Miami Dolphins. With his teammates celebrating a blocked last-minute Miami field goal, Lett tried to recover the ball, ultimately fumbling it back and gift-wrapping a chip-shot winning field goal for the Dolphins.

Super Bowl XIII, January 21, 1979

What happened: The toughest inclusion on the list, Smith's simple drop may be the most painful. Smith, in the last season of a Hall of Fame career, hadn't caught a pass all season. But with the Cowboys trailing 21-14 in the third quarter against Pittsburgh, he broke wide open in the end zone. Roger Staubach's slightly underthrown pass bounced harmlessly off Smith's hands, and instead of a sure touchdown, the Cowboys were forced to settle for a field goal. The Steelers won, 35-31.

Danny White's audible

Dec. 11, 1983

What happened: Trailing 14-10 and facing a fourth and inches from his own 49-yard line in a crucial late-season showdown against the Redskins, quarterback Danny White talked Tom Landry into letting him try to draw the Redskins offside. But with one second on the play clock, White audibled for a Ron Springs run, which resulted in a 2-yard loss. The play shifted the momentum of the game, with Landry, famed for his calm and composed demeanor, losing it, berating White on national TV and screaming "No, no, no, Danny, no!" Dallas lost, 31-10.