Capture-the-Flag played in high-traffic landmarks... inconspicuously.
Players compete in secret variations of field games like capture-the-flag or hide & seek. Games are in high-traffic landmarks (e.g. Grand Central Station or Oculus at WTC) and only the players know the game is being played. The public has no clue a game is happening all around them. Strategy wins over strength and speed. This experience forces the most competitive players to set aside an individual win for the good of the team.