Since forming back in 1960, the Dallas Cowboys have been one of the most successful teams in the NFL, as they have won 10 NFC Championships and five Super Bowls. The reason for this success definitely has a large part to do with good drafting, but many of the greatest players to play with the Cowboys have come through the free agent market. Keeping this in mind, I have formed a list of the five best free agent signings to ever play in Dallas.