In addition to the many useful magical items available to your Lords and Heroes, your knightly characters also have the option to select a number of unique Virtues which in and of themselves are equivalent to some magic items and can have a major effect on the game.
The Virtues have changed over the evolution of the game. The Virtues listed here are updated with the 6th Edition Rules.
Virtue of the Penitent- the benefit of this virtue makes it less likely for your Knightly character to run after combat. However, it also prevents the character from joining any friendly units (meanly he basically has to fight alone) which I never feel very comfortable with. I would pass up this virtue and take another one.
Virtue of Knightly Temper- a chance to gain extra Attacks? Always a great benefit. Definitely a possibility though its high Points cost may limit the virtue to only the more powerful characters.
Virtue of Heroism- If you know for a fact that your opponent is playing dragons or other Large targets, this virtue might prove most useful. Otherwise, I wouldn't bother.
Virtue of Stoicism- this virtue allows the Knight and his unit to re-roll Break tests. I like to give it to my Knight characters with the Grail Vow to make them even more resilient. Definitely a very valuable commodity.
Virtue of the Ideal- this virtue certainly helps turn your Knight into the uber-warrior but at a pretty steep price. If you do take it, try to give it to a character who will be isolated from the majority of your other units whenever possible otherwise you could be asking for trouble. I generally don't even bother with this one.
Virtue of the Impetuous Knight- this is a favorite of mine as it allows the charging unit of knights to get a slight jump start and surprise your enemy units.
Virtue of Audacity- Another great choice that helps protect the knight in battles against physically more powerful enemies. This Virtue allows the knight to re-roll any failed "to hit" and "to wound" rolls against any enemies with a higher Strength score.
Virtue of Duty- Definitely a must for larger armies however this virtue can NOT be given to the Army General and can ONLY be given once. As long as the General is alive, the model with this virtue adds +1 to combat resolution for any combat he is in. What could be better than this? I will often give this Virtue to my Army Standard Bearer or any other Paladins I may be fielding.
Virtue of the Joust- If you like to "hit 'em hard and fast" this is the Virtue for you. It allows the knight to re-roll failed rolls to hit but only when charging and using a lance (so it can't be given to a knight with the Questing Vow).
Virtue of Confidence- I like to give this Virtue to one of my more powerful characters since it forces that knight to always issue and accept challenges whenever possible. This virtue allows the knight to re-roll all failed rolls "to hit" and "to wound" which will certainly give him an edge in the combat.
Virtue of Noble Disdain- This virtue is one of my personal favorites. The virtue causes the knight to hate all enemies using missile weapons (archers, crossbowmen, etc) including war machine crews. In addition, any unit the knight has joined never takes Panic tests caused by suffering 25% casualties. I often like to give this virtue to the leader of a knightly unit that will be dedicated to hunting down and wiping out the enemy's missile batteries.
Virtue of Purity- Another great choice and at a fairly low Point cost too. This defensive Virtue allows the knight to always start the game with the Blessing of the Lady even if the army did not pray (though why they wouldn't is beyond me). In addition, the Ward save the Knight gains from the blessing is always 5+ regardless of the Strength of the attack. I recommend giving this virtue to characters with the Knight's Vow or the Questing Vow only since Knights with a Grail Vow already receive the free automatic Blessing anyway.
Virtue of Discipline- This valuable virtue prevents any enemy unit from receiving a +1 combat resolution bonus for outnumbering your knight's unit. This is a good thing since units of Knights are generally smaller in number. It does not protect the unit from fleeing if beaten by a fear-causing enemy that outnumbers them as per the rule book. (Of course you can override this glitch by giving it to a character from a unit of knights with the Grail Vow which are Immune to Psychology.)
Virtue of Empathy- The cheapest of all the Virtues in terms of Point value I tend not to use this one very often even though it is not without its own merits. The nice thing about the virtue is that it allows the Knight to forsake his mount and to be fielded on foot perhaps to lead one of your peasant militias or protect any wizards on foot. Even better, it allows Peasant units within 12" of this character (rather than the normal 6") to use his Leadership score as long as the character is NOT the General.