OK guys here is where I really need to alert you to the existence of BLOODRUSH.
Bloodrush is a game that was invented by some friends of mine for use at the LARP camp that I work at. It was originally conceived as a gladitorial game, played by human slaves for the amusement of vampire overlords (this was part of a vampire-centric universe that my friend spent a lot of time writing, all full of political intrigue and bloody betrayal and wars between human slave armies and that sort of thing). The premise was that feuding clans of vampires would use their human thralls to play blood sports against each other. The first games of Bloodrush were full-on LARP events, with cruel vampire-overlord referee characters who would liberally dish out pain and injury as punishments for fouls but just as happily turn a blind eye to an exceptionally admirable kill or play despite a little bending of the rules on the part of the players. The players of the game were human slave characters, and they were pretty developed (all individually developed by the people playing them, of course), and the teams were supposed to have certain tendencies according to the vampire lords they served (some more brutal and quick to cheat, some more cooperation-oriented, some rivalries, etc.)
Nowadays we just play Bloodrush as a combination sword game/sport ... it's a favorite among the more athletic campers. We don't have full-on adventure games that involve Bloodrush too much anymore, but we still play.
Basically the premise of the game is as follows:
The field is about 100 feet by 40, with end zones 15 feet deep on each end. There is a small target an additional 20 feet behind the border of each end zone. Scoring points is accomplished by gaining possession of the ball and carrying it into the opponent's end zone, a touchdown worth 1 point, or by throwing the ball and hitting the target behind the opponent's end zone, which is worth 3 points. A player may not enter the opposing end zone unless they are in possession of the ball, however, so no passing into the end zone (just about anything else goes, though).
Teams consist of 7-10 players each. No more than 6 players from each team are allowed on the field at any one time (including dead bodies, but I'll get to that). During play, players may not cross the boundaries of the field unless they are dead and dragged off. If the ball goes out of bounds, an off-field player from one of the teams retrieves it and throws it back onto the field (once an off-field player has possession of the ball they cannot move and must throw, and they may throw to off-field teammates as well as onto the field). Substitutions between on-field and off-field players can happen in the time in between points, but only across the boundary of the end zones, not the playing field itself. One player from each team is designated the cleric, and is the only team member who can cross on and off the field during play. The cleric has the capacity to heal injuries of varying severity and has a limited number of resurrections (usually clerics have 4 Heal Minor, 4 Heal Serious, 4 Heal Critical, and 4 Resurrect per half). If the cleric is killed during play, a team will obviously be at a huge disadvantage for the rest of that point but once a score has been made they may trade in a score point to resurrect them before play resumes.
The ball can be transported across the field by any means ... carried, dribbled (like either basketball or soccer), kicked, thrown, anything. HOWEVER, and this is the important part that makes the game so much fun, IF a player is in possession of the ball (which means they are carrying it or it is otherwise under their direct control), it is perfectly legal to KILL THEM.
See, each team starts with one sword, and there are swords, daggers, and various other implements of violence scattered around the field at the start of play. Any player except the cleric may use a sword, and anyone can use a dagger.
It's important to note that weapons will wound and kill regardless of whether or not they are used legally. If the ref isn't looking, you can totally shank the opposing player next to you and get away with it. And even if the ref sees you kill or maim your opponent illegally, and you get punished, it's up to the fickle whim of the ref whether or not the fouled player is healed. This makes for an interesting array of strategies revolving around how to get away with cheating. Basically, it makes for an AWESOME gladiator game because the spectators get to see rampant violence while also watching players with exceptional skill win in possibly-legitimate ways. And plenty of the killing in Bloodrush IS totally legal!
The last important part is how refereeing works. The referee was originally conceived as a vampire overlord of extreme power, and has more or less absolute dominion over the field. This includes SPACE AND TIME. What this means is that the way fouls are treated is as such: when a referee sees something that warrants a punishment, they blow a whistle. This signifies TIME STOP. All players are to immediately freeze in place and close their eyes (failure to comply is obviously punishable by whatever the ref sees fit). The ref, sequestered in an objective state outside space and time, has free rein to move the ball around, move players around, inflict punishments, or heal players that have been fouled in exceptionally flagrant ways. More often than not the ref will do a little of all of these each time they stop time. Using the whistle to effectively pause all game activity, move things around, and start them back up again creates an effect of "instantaneous" change in the game ... let's say I'm running towards the ball and I get hit with a sword and the ref sees it and blows the whistle. The ref will probably injure or kill the offending player, might heal/resurrect me partially or fully (if they're feeling nice), and will probably move the ball somewhere else so that there is a moment of confusion when time resumes and nobody knows where the ball is. This allows the ref to rebalance the gameplay more or less at will, which makes for some interesting interactions between refs and teams that play fast and loose with the rules.
(While the magical-power-over-space-and-time thing was originally part-and-parcel of the vampire-overlord roleplaying universe, it also serves an essential purpose in casual games in that it resolves ambiguities. If someone is fouled as they score, for instance, the time-stop period allows the 2-3 refs on the field to decide the call without allowing input from players to get in the way. It also makes sure that nobody is able to use a tempo advantage gained illegally to score a point they don't deserve. When it gets right down to it, though, it really needs to revolve around the fact that the referee is an absolute authority, so the vampire-overlord flavor always helps a lot, especially if a good roleplayer is taking advantage of the high-status role.)
There are a few more things to note ... for one thing, once a point is scored, teams have 10 seconds to get all their living players back to their end zone, all their dead players off-field, and end up ready to play with 6 on-field players in their end zone when the ball is put back into play. Failure can be penalized in the loss of score. Also, weapons cannot under any circumstances be carried off-field, and while on-field players technically can injure or kill off-field players if their weapon's reach is long enough and their opponent gets too close to the boundary, such instances are rare. Finally, it is prohibited to hit the ball with a weapon ... the vampire overlords fashioned those balls from the finest human hide, and they are prized! Destroying them is often punished with severe injury, death, or some form of vampire curse such as slowness, blindness, or feeblemindedness.
The game obviously hinges a great deal on theatrics. If you're playing and you feel yourself being hit with a foam weapon, NO MATTER WHAT you have been injured or killed. The severity of the injury is entirely acted out, improv style (we teach workshops explaining how to react to foam weapons beforehand, obviously ... although by the time people play Bloodrush they're usually pretty familiar with how that part works). If you get cursed by a vampire for committing a foul, you act out the curse. If you've been killed, you don't scream for a cleric, and if you've been really seriously injured, you probably just scream in general, or maybe cough and convulse a bit. Likewise, if you don't have the theatrical capacity to respect the authority of the ref as an ABSOLUTE power (contesting calls, for instance, or failing to obey), you're likely to be punished profusely (although maybe that's what your character would do, I don't know). Bloodrush is very much acted as much as it is played.
Simply put, this game is more frenetically intense and fun than anything I've ever played. There's an implicit degree of cooperation underlying the theatrical aspect of things (everyone agrees to act out wounds and such fairly), even while the competition during gameplay can be crazy fierce and can lead to some very dirty plays. There's a really deep level of strategy involved, too ... placing your team in the right areas of the field, playing to each individual player's strengths and weaknesses, targeting specific opposing players, using throwing/passing strategies instead of rushing/carrying strategies, which weapons you claim, etc.
It's a fucking fantastic game and it blows most organized sports completely out of the water when it's done right.