The decathlon. Ten events over two days, often in the intense summer heat.
Basically there's two kinds of decatletes: Strong guys who have become decent runners and jumpers and fast guys who have become decent throwers. Is it worth it for a strong guy to really exert himself on the pole vault for a few points when it might sap his strength in the javelin? Can the fast guys stave off the big guys in the shot put and discus? With two days of competition and a variety of events, there's plenty of time to discuss the strategy.
Finally, the winner is not only given an Olympic gold medal, but also can rightfully claim the title World's Greatest Athlete.