Fighter archetype
Thunderstriker
Source: Ultimate Combat, p. 48
The thunderstriker adopts an unusual fighting style, gripping a heavy weapon with both hands and switching to a defensive posture with weapon and buckler, lashing out with the shield with surprising speed and power.
Strapped Shield (Ex) level 3
Replaces Armor Training.
At 3rd level, a thunderstriker takes no penalty on attack rolls when using a weapon in two hands while wearing a buckler. This ability replaces armor training 1.
Hardbuckler (Ex) level 7
Replaces Armor Training.
At 7th level, a thunderstriker may make shield bash attacks with a buckler as if it were a light shield. This ability replaces armor training 2.
Knockback Smash (Ex) level 11
Replaces Armor Training.
At 11th level, when a thunderstriker uses his buckler to attack, he gains a bonus equal to the enhancement bonus of the buckler on both attack and damage rolls. This ability replaces armor training 3.
Hammer and Anvil (Ex) level 13
Replaces Weapon Training.
At 13th level, a thunderstriker suffers only half the normal penalties for two-weapon fighting when using a buckler as his off-hand weapon. This ability replaces weapon training 3.
Buckler Defense (Ex) level 15
Replaces Armor Training.
At 15th level, a thunderstriker retains partial use of his buckler even when using a weapon in both hands or in each hand (rather than losing his shield bonus until the beginning of his next turn). He gains a +1 shield bonus to AC and may apply the benefits of any feats he knows that require the use of a shield, but does not benefit from any magical properties his shield may possess. This ability replaces armor training 4.
Balanced Bashing (Ex) level 17
Replaces Weapon Training.
At 17th level, a thunderstriker no longer suffers two-weapon fighting penalties when using a buckler as his off-hand weapon. This ability replaces weapon training 4.
Improved Buckler Defense (Ex) level 19
Replaces Armor Mastery.
At 19th level, a thunderstriker does not forfeit his shield bonus to AC from a buckler when fighting two-handed. This ability replaces armor mastery.