Feat Breakdown
L1 : Power Attack
F1 : Two Weapon Fighting
H1 : Improved Shield Bash
F2 : Weapon Focus : Spiked Heavy Shield
L3 : Iron Will
F3 : Step Up
L5 : Combat Reflexes
F4 : Improved Two-Two Weapon Fighting
L7 : Shield Slam
F5 : Improved Bull Rush
L9 : Greater Bull Rush

Feat Bonuses
Power Attack
You can choose to take a –1 penalty on all melee attack rolls and combat maneuver checks to gain a +2 bonus on all melee damage rolls. This bonus to damage is increased by half (+50%) if you are making an attack with a two-handed weapon, a one handed weapon using two hands, or a primary natural weapon that adds 1-1/2 times your Strength modifier on damage rolls. This bonus to damage is halved (–50%) if you are making an attack with an off-hand weapon or secondary natural weapon. When your base attack bonus reaches +4, and every 4 points thereafter, the penalty increases by –1 and the bonus to damage increases by +2. You must choose to use this feat before making an attack roll, and its effects last until your next turn. The bonus damage does not apply to touch attacks or effects that do not deal hit point damage.

Two-Weapon Fighting
Your penalties on attack rolls for fighting with two weapons are reduced. The penalty for your primary hand lessens by 2 and the one for your off hand lessens by 6.

Improved Shield Bash
When you perform a shield bash, you may still apply the shield's shield bonus to your AC.

Weapon Focus [Spiked Heavy Shield]
You gain a +1 bonus on all attack rolls you make using the selected weapon.

Iron Will
You gain +2 on Will saving throws.

Step Up
Whenever an adjacent foe attempts to take a 5-foot step away from you, you may also make a 5-foot step as an immediate action so long as you end up adjacent to the foe that triggered this ability. If you take this step, you cannot take a 5-foot step during your next turn. If you take an action to move during your next turn, subtract 5 feet from your total movement.

Combat Reflexes
You may make a number of additional attacks of opportunity per round equal to your Dexterity bonus. With this feat, you may also make attacks of opportunity while flat-footed.

Improved Two-Two Weapon Fighting
In addition to the standard single extra attack you get with an off-hand weapon, you get a second attack with it, albeit at a –5 penalty.

Shield Slam
Any opponents hit by your shield bash are also hit with a free bull rush attack, substituting your attack roll for the combat maneuver check (see Combat). This bull rush does not provoke an attack of opportunity. Opponents who cannot move back due to a wall or other surface are knocked prone after moving the maximum possible distance. You may choose to move with your target if you are able to take a 5-foot step or to spend an action to move this turn.

Improved Bull Rush
You do not provoke an attack of opportunity when performing a bull rush combat maneuver. In addition, you receive a +2 bonus on checks made to bull rush a foe. You also receive a +2 bonus to your Combat Maneuver Defense whenever an opponent tries to bull rush you.

Greater Bull Rush
You receive a +2 bonus on checks made to bull rush a foe. This bonus stacks with the bonus granted by Improved Bull Rush. Whenever you bull rush an opponent, his movement provokes attacks of opportunity from all of your allies (but not you).

Standard Attack : Main Hand Shield Bash
+9 Base Attack Bonus
+4 Strength Modifier
+2 Weapon Training
+1 Weapon Focus
+1 Bashing Ability
-6 Dual Wielding
+2 TWF Feat
Total : +13

High BAB Extra Attack : Main Hand Shield Bash
+4 Base Attack Bonus
+4 Strength Modifier
+2 Weapon Training
+1 Weapon Focus
+1 Bashing Ability
-6 Dual Wielding
+2 TWF Feat
Total : +8

Standard Attack : Off Hand
+9 Base Attack Bonus
+4 Strength Modifier
+1 Weapon Training
+1 Masterwork
-10 Dual Wielding
+6 TWF Feat
Total : +11

ITWF Extra Attack : Off Hand
+9 Base Attack Bonus
+4 Strength Modifier
+1 Weapon Training
+1 Masterwork
-10 Dual Wielding
+6 TWF Feat
-5 Second Attack
Total : +6

Standard Attack : Main Hand
1d6 Weapon Damage
+4 Strength Modifier
+2 Weapon Training
+1 Bashing
Total : 1d6+7

Crit 20x2

Standard Attack : Off Hand
1d4 Weapon Damage
+2 Strength Modifier
+1 Weapon Training
Total : 1d4+3