Simple Q&A D&D 3.5 (by RAW) XXIII

[Garret Dorigan]

A379 Contention/Correction/Clarification-

Ask your DM.

If an Unarmed Strike is a Natural Weapon (upper case, defined game term) with the special rule of it gains Iterative Attacks like any other Simple weapon, any Full-Attack Action made by any character could be followed by an Unarmed Strike at their full BAB -5 to be used as a Secondary Natural Weapon.

This interpretation gives leeway toward abuse.

The interpretation that it is a Simple weapon, treated as a natural weapon (lower case, referential to concept) for magical effects and enhancements, does not muddy the waters of the system as it stands. While not in a game book, Skip Williams, co-designer of D&D 3.0 wrote an article on the Wizard's website doling out info on the mechanics of Unarmed Strikes. In part one, he defines an Unarmed Strike as such:

Unarmed Attack/Unarmed Strike: These two terms are used interchangeably to describe an attack with an appendage that is not a natural weapon, such as a human's fist. An unarmed attack usually deals nonlethal damage and provokes an attack of opportunity from the creature being attacked.

In part two of this article, he supports the second interpretation with the following:

Before we move on, it's worth pointing out that a character making an unarmed attack, even with the Improved Unarmed Strike feat, does not have natural weapons. Nor is a natural weapon a substitute for the Improved Unarmed Strike feat.

As we saw in Part One, unarmed strikes allow iterative attacks and natural weapons do not.

A feat that requires natural weaponry as a prerequisite, such as Multiattack, doesn't work with unarmed strikes. Likewise, having a natural weapon is not a substitute for the Improved Unarmed Strike feat. For example, you don't meet the Improved Unarmed Strike prerequisite for the Deflect Arrows feat if you just have a natural weapon.

There is material to support both sides of the argument though, so as such define the rules of Unarmed Strike as it pertains to the game that you are in with your DM.