So far the only thing anywhere properly implement is the tournament system I think I've mentioned a few times beforehand. Obviously, medieval tournaments weren't some kind of non-stop gladiatorial games where you could just wander in. In fact, there were a number of different formats, but in all cases a tournmaent was a grand meeting of chivalry, announced far and wide, where renowned knights and young squires would compete for fame, honour, and just for the hell of it (and also for more baser reasons, namely the rich ransoms they could obtain from defeated opponents). Now, representing all the ceremonial of a tournament might possible in M&B, but it would likely take me a couple of years to do so. Worse, I don't seem to be able to know who the player's knocked out in a melee, although I can find how many people s/he defeats; and I can't make lances shatter after delivering a couched lance attack, much to my dismay. So my dreams of super-accurate tournaments have a dent in them.
What I've settled on is a kind of simplified tournament instead. Tournaments will periodically be organised in some town or important castle (curently there's one somewhere every 10.5 days on average, I may change that later); the player will be able to find out where and when the next tournament will be held by asking the innkeepers (well, they need to be useful for something--maybe later there will be heralds for that kind of stuff). Then he'll be able to sign up for the tournament up to three days in advance. There are two sections, noble and common, and which you can participate in will be strictly determined by your status. No jousting commoners or wrestling lords, please.
For the nobles you will be expected to wager something (effectively an entrance fee), and if it's your first tournament you'll have to ransom your helm from the tournament's chief herald--this is a one-time occurence, once you've particpated in a tournament it won't happen again. The nobles will have three different types of events they can participate in, although actual jousting is not currently available (I don't have the appropriate scenes and stuff yet, and I have some coding stuff to figure out as well). The other two are the melée, the chief event, and one-on-one combat on foot. In the mélée there are two teams, the Challengers and the Defendants. Participants are expected to furnish their own horses, armour, and optionally shields, but must use tournament-approved lances, rebated swords and underweight maces. The goal is quite simple--batter the other side into submission. There are three ways to win fame, honour and fortune: simply by being on the winning team, by capturing (knocking out) as many knights as possible so as to collect ransoms and win a reputation for badassery, and by having the ladies, damsels and judges of the tournament proclaim you to have been the best fighter of the event (knocking out more opponents and being on the winning team both improve your chances of this, but it's never certain--sometimes the judges are just biased, and the ladies may vote for the cutest knight or something). However, if you're knocked out you will have to pay a ransom. The one-on-ones are similar, but on foot and without the lance; after the mélée you will be challenged to them by other knights (the more you draw attention to yourself, the more challenges you'll receive). Here you can only make gains through ransoms, and the prestige rewards are less. Maybe one day all the participants will be named and you'll be able to issue your own challenges, but not yet.
For peasants things are simpler: you have only two events, staff-fighting and archery, although I haven't yet figured out how to make the archery contest work properly so only staff-fighting works. No armour, one-on-one, and you've got to fight bouts against successively tougher opponents to become the event's champion, which will win you prizes. These are more modest than for the nobles, but then you don't have any entry fees either.