There is a long term debate surrounding what penalties are associated with making an AoO with an off hand weapon. Some people maintain that if you take an AoO with your off-hand weapon, you must take the TWF penalties (I will refer to this as Side 1). Others claim you only take the penalties if you use the full attack action to get extra attacks using the off hand weapon (I will refer to this as Side A).).
I don't see it this way at all. A weapon used for an AoO that is in your off hand, takes a -4 penalty to attack. That's it. Nothing else. It matters not if you have been, or even are planning to TWF. The AoO action is independent of other things you have done, or will do in the round because it happens out of your turn (Other penalties apply for Power Attack, Combat Experitse, etc).
If you take "in this way" to mean whenever "you wield a weapon in your off hand", then you are on Side 1. If you take "in this way" to mean whenever you "get one extra attack", then you are on Side A.
I believe that there should be no Side 1 at all. Side 1 is a different animal from Side A. Having a weapon in your off hand, or a wand, or a potion, or a shield, has no bearing on your primary hand's attack if you are only using the primary hand to attack with. Just having another item in your off-hand does not constitute a penalty.
Side A, as you call it, refers to making TWF attacks only. An extra attack for an AoO is always made at your best BAB bonus (minus Power Attack etc.). Again, if the character purposefully chose to attack with the off hand weapon for the AoO, they would take the NORMAL -4 penalty for doing so with the off hand.
If you are trying to be consistent, these two different interpretations have a pretty wide number of side effects. For example, with Side A's POV, a character can wield daggers in both hands and interchange attacks between the daggers as desired, as long as they only get the normal number of attacks.
This is not the case by the RAW. Clearly, you must take penalties if attacking with your off hand weapon as a full or standard action, or when making TWF attacks.
With Side 1's POV, this would require taking penalties, regardless of whether or not the character makes any extra attacks.
This is not the case by the RAW. Clearly, you only take penalties when attacking with an off hand weapon as a full or standard action, or if making TWF attacks. You do not take a penalty just for having two weapons in hand.
This makes Side A seem better from a balance/options standpoint. OTOH, Side A's side allows a character to sit around 24/7 with a reach weapon just to take AoOs and never take any penalties.
I wanted to comment on this... I'm not sure what having a reach weapon (assuming it is two handed I suppose) has to do with a discussion on off handedness. It seems to be a completely different animal.
Side 1's view stops this. This makes Side 1 seem better from a balance perspective.
Except that Side 1 is not an option considering the RAW.
I believe that the confusion comes from individuals who believe that there is no penalties for
using an off hand weapon. Just go look in the glossary and the other three locations in the rules that mention off handedness just slip into place.
To be clear, off hand weapon attacks take a -4 (for full, standard, AoO, and extra attacks). TWF attacks have a seperate chart to follow
because you are fighting with both hands. These are two different circumstances.
Therefore, you must, at the time of character creation, be specific about handedness.
Aluvial