For me, it's the Giants converting every third down in the second half as they held the ball and ran the clock down. I only rewatched the last few minutes just two years ago. It's still painful.
That was the obvious one we should have won. But many forget that in the fourth one, the Bills were ahead at halftime and playing well against the Cowboys, but a Thurmon Thomas fumble early in the third quarter changed the momentum of that game. The Cowboys quickly scored to take the lead, and it went downhill from there. We had a good chance to win that day without that fumble.