Cavalier Champion is the highest rank of Cavalier. It is the Knight errant. Often the Joust Master.
This Knight can wear plate-mail armor and wear a shield. He or she can also use a lance while in mounted combat or a mace/sword/axe and shield combination. On the ground they can use ANY weapon except for a longbow. (NOTE: the Cavalier Champion CAN use a crossbow for ranged while unmounted.)
The Cavalier Champion is also granted a special set of armor upon reaching this rank. This armor is enchanted and allows for D4 and M3. It is commonly made of a special metal like Mithril.
They also get a special Lance and either an axe (or hammer or mace or sword) that allows for critical strikes.