reapersaurus said:
I consider grapple checks to be a melee attack.
Therefore, Power Attack would apply to them, and fighting defensively, also.
If you consider them seperate from an attack just because it's referred to as a "grapple check", than you're inviting problems such as getting a penalty that doesn't hurt you (fighting defensively) or taking a penalty and getting no benefit (Power Attack).
From SRD
If You’re Grappling
When you are grappling (regardless of who started the grapple), you can perform any of the following actions. Some of these actions take the place of an attack (rather than being a standard action or a move action). If your base attack bonus allows you multiple attacks, you can attempt one of these actions
in place of each of your attacks, but at successively lower base attack bonuses
"In the place of" means they are not attacks. On actions taken "in place of each of your attacks" you can not use feats and abilities that modify your attacks. But there are two primary way of damaging your opponent one of which is an attack the other is not.
From SRD
Attack Your Opponent: You can make an attack with an unarmed strike, natural weapon, or light weapon against another character you are grappling. You take a –4 penalty on such attacks.
You can’t attack with two weapons while grappling, even if both are light weapons.
This is an attack so you can use abilities that modify your attacks. I forgot this option when making my first post.
From SRD
Damage Your Opponent: While grappling, you can deal damage to your opponent equivalent to an unarmed strike. Make an opposed grapple check in place of an attack. If you win, you deal nonlethal damage as normal for your unarmed strike (1d3 points for Medium attackers or 1d2 points for Small attackers, plus Strength modifiers). If you want to deal lethal damage, you take a –4 penalty on your grapple check.
Exception: Monks deal more damage on an unarmed strike than other characters, and the damage is lethal. However, they can choose to deal their damage as nonlethal damage when grappling without taking the usual –4 penalty for changing lethal damage to nonlethal damage.
This is not an attack but a special grapple option. So you can not use abilities that modify your attacks when using this option.
You can also preform these action in place of your attacks.
From SRD
Escape from Grapple: You can escape a grapple by winning an opposed grapple check in place of making an attack. You can make an Escape Artist check in place of your grapple check if you so desire, but this requires a standard action. If more than one opponent is grappling you, your grapple check result has to beat all their individual check results to escape. (Opponents don’t have to try to hold you if they don’t want to.) If you escape, you finish the action by moving into any space adjacent to your opponent(s).
Pin Your Opponent: You can hold your opponent immobile for 1 round by winning an opposed grapple check (made in place of an attack). Once you have an opponent pinned, you have a few options available to you (see below).
Break Another’s Pin: If you are grappling an opponent who has another character pinned, you can make an opposed grapple check in place of an attack. If you win, you break the hold that the opponent has over the other character. The character is still grappling, but is no longer pinned.
None of these options are attacks but they can all be preformed in the place of attack wile in a grapple.
Here is another option that is IMO unclear whether it is an actual attack or not.
From SRD
Use Opponent’s Weapon: If your opponent is holding a light weapon, you can use it to attack him. Make an opposed grapple check (in place of an attack). If you win, make an attack roll with the weapon with a –4 penalty (doing this doesn’t require another action).
You don’t gain possession of the weapon by performing this action
