hong said:Not really, because you still have to attack with the shield to get the defender benefit.
SRD
As a free action, the wielder chooses how to allocate the weapon’s enhancement bonus at the start of his turn before using the weapon, and the effect to AC lasts until his next turn.
Evilhalfling said:Do you have to attack every round with a defending weapon to gain the AC bonus?
kjenks said:In the old 3e FAQ, there was an entry saying that you must attack with a defending weapon to get its AC benefit, but that entry wasn't incorporated in the 3.5e rules.
And yes, you can wield the defending dagger in your off-hand, with no attack penalties on the weapon in your other hand (following the PH rules for TWF and the example of the 3.5e FAQ entry about a longspear and armor spikes to see that there is no TWF penalty unless you actually attack with the off-hand weapon).
Try this shield: +1 animated heavy steel shield with +1 defending shield spikes.
Fortain said:This leads me to believe that, if you use the Defending ability of the spiked shield, not only do you suffer the penalty for using two weapons, but you also lose your shield bonus to AC, since you're technically "using the shield as a weapon" to gain the Defending AC bonus.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.