You can use a dwarven chain-flail with only one hand.

Prerequisites: Two-Weapon Fighting, base attack bonus +4, proficiency with the dwarven chain-flail.

Benefit: You can use a chain-flail as a one-handed weapon. When using it one-handed, changing whether it’s a normal or reach weapon is a full-round action. If you have the Darting Viper feat, changing its reach is a move action.

Normal: A dwarven chain-flail requires two hands to wield.