I'm planning on a Centaur Knight.
[sblock=Backstory]
In a frontier town on the edge of a great forest, the humans began to chop trees and clear land to extend their agricultural potential and feed hungry mouths. A tribe of centaur who had been on the land before their arrival objected, sending an emissary to ask for an end to the activities. The envoy was received with open hostility by the suspicious and bigoted magistrate, and upon making his plea in more impassioned and forceful tones the order was given for his execution. Before long the village was in open war against the centaur tribe. They called for reinforcements from the nearest town, pleading that they were under attack by savage natives of the forest who wouldn't listen to reason.
A force of knights from the town's chapter of the crown's Argent Order arrived as their reinforcement, and the impetuous young commander leading them took the villagers and their magistrate at their word. He launched a full-scale assault on the centaur tribe and with superior numbers, equipment and training his force soon won the day. It was only after the tribe's numbers had already been decimated that one of the centaur, grievously wounded, finally let go of his pride long enough to plead for mercy just before he died - not for himself, but for his tiny daughter.
Such selfless sentiment struck deep, undermining the righteous anger of the commander, and he called a halt to the attack. Sheathing his sword and approaching another of the survivors, he demanded that the centaur explain events as he understood them. He was mortified by what he heard, as he realised the depth of the mistake he had made. He knew there was nothing he could do to make his actions right, with the tribe already shattered, but he resolved to do all he could. Finding that the centaur child had no relations or friends to take care of her among the survivors he started by taking her away with him, determined to give her the best possible life he could.
He went further as well, appealing to the King and seeing that the village magistrate was unseated and harshly punished, and that in future the village would abide by the wishes of their fallen foes and live in harmony with the land.
The centaur girl, meanwhile, he brought up as his own daughter. It was certainly an extraordinary arrangement, but for a relationship that had started so unhappily it brought both of them a great deal of joy. The girl, named Cele, never knew why it was that this man had taken her in and fostered her, but she loved him and was happy under his guardianship and tutelage. He taught her what he knew best - arms, and the code of chivalry. In putting special stress on the latter, perhaps he hoped to make up for his own dereliction of it in regard to her people.
Happily for him, he never had to explain the circumstances of her adoption; he was killed in action when she was still young. She was allowed to stay on in the Order - she had many friends there, as had her late foster-father, and she was after all one of its most promising initiates despite the incongruity of a centaur in a knightly order. It was not easy for her to achieve acceptance, but for her skill and diligence she did at least achieve respect. She was a fierce warrior, loyal to the Order above everything, and she quickly also developed skills that made her especially valuable - her heritage gave her a natural empathy for the wild which she was encouraged to develop, since a knight who could track, navigate and interpret the weather would always be an asset on any protracted mission.
And yet for all that, not all were ready to accept her presence in the Order. Her father had had enemies too, and ultimately it was one of those who was her downfall. He let slip an unpleasant remark insinuating the true reasons for her adoption, and in her passion she had challenged him then and there to a duel.
Duelling was of course strictly forbidden between members of the order - a superior had immediately stepped in to prevent it.
It is not so easy to truly quench a passion though; Cele managed to get a message to her adversary naming a time and place, and he accepted a day later with a proviso changing suggested the location. She agreed, and slipped out from her quarters in the dead of night with her full wargear to make her way to the appointed spot. Her enemy was nowhere to be seen. After a minute's impatient waiting there came a heavy impact on the back of her skull and then a long period of blackness, slipping in and out of consciousness but with the darkness always constant and accompanied by the sensation of movement.
When finally she was set loose, she had been quietly disposed of. To kill her would have been too risky - so she had simply been cast away, swept under the rug of the multiverse.[/sblock]
No detailed crunch yet, but I have some ideas. She'll be a pure Knight as far as her class levels are concerned - which means Centaur 4/Knight 6 at the start, with a +2 LA (though I guess I could consider buying that off; might be smart). Statistically she'll be based mostly around the rather nice synergy between the Knight class with it's 'tanking' abilities and a Large size character with its larger reach. I'll be aiming to take the Large and in Charge feat if you'll allow it (from Draconomicon; basically allows an opposed check any time you make an AoE for somebody entering a threatened square. If you win, they're pushed back 5'). Otherwise she'll be sword and board style, with a high Str and Con and a very good armor class too I hope thanks to Natural Armor from her race and Heavy Armor (probably mithril, to take advantage of the Knight's Armor Mastery Ability from the start). She'll be more focused on a strong defence than really dishing out the pain, though she'll also be no slouch at whacking stuff with a sword, particularly on a charge. I'm considering Two Weapon Fighting/Improved Shield Bash/Shield Charge (Complete Warrior) to improve offensive capability, though obviously there's a heavy feat investment involved; it might well not be worth it.
Finally she'll bring some wilderness survival to the group, with a good Survival check and the Track feat.