Chivalrous (3.5e Flaw)
From D&D Wiki
Whether due to a vow or natural inclination, you do not fight women.
Effect: You may not attack (or aid another in attacking) a female of your race. Furthermore, you take a -4 penalty to attacks against female humanoids of any sort.
Roleplaying Ideas: Cadogan whipped his blade free of the corpse and spun to face his next assailant. A glimpse of feminine eyes flashed above the veil that covered the assassin's face. "Blood and ashes." Cadogan dodged backward from the spinning whirlwind of knives the woman launched at him. He Swung his sword wildly between them, seeking not to kill but to deter. How did it always come to this? He prayed this assassin at least would retreat before he was forced to shed her blood. The very thought of it stabbed his mind almost as painfully as those rapidly stabbing daggers might. He spared glances from side to side, looking for some method by which to make a withdrawal.