mostholy2 said:If fighting defensively incurs an attack penalty, I would rule that it would mimick the case of VoP attack bonus and only apply on any rolls described as "attack rolls" not strength or grapple rolls. Therefore fighting defensively affects initial touch attacks for special attacks, the attack rolls for disarm and sunder, but does NOT affect grapple check or trip str. check rolls.
Earlier, you talked about Bob the fighter, who was
unconscious and later woke up, prone, to find Grog the orc
standing in his space. You said Bob has to stay prone so
long as he remained in Grog’s space, and that Bob would
provoke an attack of opportunity upon leaving that space.
Suppose Bob made a grapple attack on Grog? He can
grapple Grog, can’t he? Bob would be at a negative for
being prone but would not provoke an attack of
opportunity, would he? Assuming Bob establishes a hold on
Grog, how long does the prone penalty last?
Sure, Bob can grapple Grog. Bob’s initial grab attack
provokes an attack of opportunity from Grog unless Bob has
the Improved Grapple feat or some other circumstance prevents
Grog from threatening Bob. (For example, Grog would not
threaten Bob if Grog were wielding a reach weapon.) If Grog
deals damage to Bob with an attack of opportunity, Bob’s
grapple attempt is over.
If Grog doesn’t damage Bob, Bob’s initial touch attack
would suffer a –4 penalty for being prone. If the grab succeeds,
Bob is still prone and still suffers the –4 penalty for being
prone for the ensuing opposed grapple check. [...]
kjenks said:The PH says flat-out that grapple checks are like melee attack rolls
SRD said:A grapple check is like a melee attack roll. Your attack bonus on a grapple check is:
Base attack bonus + Strength modifier + special size modifier
mostholy2 said:So taking this argument one step further, if you have an enchanted or masterwork weapon (or anything) that gives +X to attack rolls, the +X would be applied to all "attack rolls" including, opposed disarm and sunder rolls when using the weapon (or item).

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