We can get into a debate about which flops were more important or more outrageous, and it would be a good debate, full of phantom contact and excruciated faces. But I challenge you to find one that is as great as this one. It comes to us from a Copa Sudamericana match in Sao Paolo between Corinthians and Universidad de Chile.
After the ball goes out of bounds, a player for Universidad de Chile motions for the Corinthians ball boy to give him another so he can throw it back in play, and the ball boy simply drops it instead of handing it over. It's the sort of typical gamesmanship you see all the time, but the player didn't appreciate it, and gave guy a little shove. Then the ball boy does something magical: he appeals to the fictitious official refereeing interactions between players and ball boys and acts like this shove to his chest has triggered some kind of heart attack. He slowly goes to ground, out of sight.
Almost immediately after he begins this charade, he loses heart. He seems to recognize fairly quickly that this is a ridiculous thing he's decided to do and rather than really sell it with a full flop, he looks like he's doing the old pretend-to-walk-down-a-flight-of-stairs-behind-the-couch routine.
When you go to a sporting event, certainly a soccer match, you are at least generally prepared for the possibility that one or more players will try to draw a foul/penalty by exaggerating an offense. What cinches this as the greatest flop, however, is the twist: you couldn't possibly have anticipated that the ball boy—a ball man, if we're being technical—would simulate a violent altercation with a player. That he didn't fully commit to the bit is just the icing on the cake.
Corinthians beat Universidad de Chile, 2-0.