Sports come in all levels of intensity. Basketball, American football, and rest-of-the-world football (aka soccer) fans all love to believe that their sport of choice is the most hardcore and dangerous. None of these hold a candle to combat sports.
Traditional martial arts in which contestants fight one another without weapons need little explanation. Though particulars change a bit depending on the style of fighting, you generally follow the rule of trying to hit your opponent more often and more powerfully than they hit you. Fairly self-explanatory, sure, but mastering it takes years. But what is perhaps more intriguing is when the fight does involve weaponry and how the fighters spar without lopping off each other's heads like Roman gladiators.
Many traditional swordsmanship styles, such as Kendo and fencing, are still practiced today and fuel highly-publicized events. Then there's SCA heavy combat, which is more akin to intense, live-action role-playing because contestants use the "honor system" for scoring points.
The next level of badassery is Historical European Martial Arts — though the name is now a misnomer as the sport allows use of a wide-variety of weapons from many eras and cultures. Training begins with wooden or plastic weaponry that can be purchased from sites like Purpleheart Armory, but when the fighter is ready, it's time to grab their steel and enter a Combat Con tournament.
There are several championships held for different styles of weaponry: Longsword, sword and buckler, and rapier are just a few of many.
All participants must wear proper armor, the weapons must be dulled, and all commands from the referees are final. Shy of that, the fighters have 90 seconds per match (or until a maximum score has been reached) to make their ancestors proud through combat.
From here, you move onto to team fights as facilitated by the International Medieval Combat Federation. Here, teams of up to 16 combatants enter to fight for their nation's glory using actual weapons and actual armor.
The objective here is to knock all of your opponents to the ground. The rules are simple: follow instruction from the referee and don't cause unsportsmanlike harm to or remove any protective gear from an opponent.
So... who's down?