Einhander( Player's Handbook II, p. 94)
[Fighter Bonus Feat, Tactical]
You excel at wielding a one-handed weapon while carrying nothing in your off hand.
Tumble 6 ranks, base attack bonus +6,
If you are fighting with a one-handed weapon or a light weapon and carrying nothing in your off hand, the Einhander feat grants you access to three special tactical maneuvers.
Narrow Profile: You can tuck your arm behind your back and offer a narrow profile when you concentrate on defense rather than offense. You gain an additional +2 dodge bonus to AC when fighting defensively or using the total defense action.
Off-Hand Balance: You use your off hand to balance yourself while performing acrobatic maneuvers. After you successfully strike an opponent, you gain a +2 bonus on Tumble checks to avoid his attacks of opportunity until the start of your next turn. When you flip and roll out of harm's way, you use one hand to keep your balance and your other hand to keep your weapon trained on your foe.
Off-Hand Swap: With a flourish, you flip your weapon into the air, catch it in your off hand, and continue to press the attack. When you use this maneuver, you must first take a full attack action to strike an opponent at least twice. On your next turn, you can make a special feint as a free action, using Sleight of Hand rather than Bluff. Your opponent uses the standard rules for resisting a feint. Once you use this maneuver against a particular opponent, whether it succeeds or fails, you cannot use it against him again.
A fighter can select Einhander as one of his fighter bonus feats.