10. Dallas Cowboys (1971)
John Mackey scored a controversial and possibly illegal touchdown in this game. It came from a Johnny Unitas pass and also gave the Cowboys something to complain about. However, for all of their excuses, Dallas was sloppy and ineffective. Jim O’Brien kicked the winning field goal with five seconds left to play. In truth, the Colts earned the win.

Dallas held a 13-6 lead at halftime but had one of the worst choke jobs in their history. A pair of interceptions proved crucial as both set up Baltimore scores. Tom Landry admitted that the Cowboys were their own worst enemy. This went down as one of the least-entertaining Super Bowl games ever because both teams were sloppy (via N.Y. Times).