Questions on power attack

[Dirkwolf]

I haven't been able to find anything regarding one of the questions I have so I apologize if i'm re-asking something that's already been asked.

My first question is, say you have multiple attacks in a round. For the sake of arguement lets say I have 3, 2 at +11 and the last at +6. Could I take the first 2 without power attack and the last one with?

My friend says that you can because as power attack states "You must choose to use this feat before making an attack roll". So you make the first 2 attack rolls without taking power attack and when your third attack roll comes around you can then use power attack for it. Making the to hits 11, 11, and 5 (or less depending on your BaB) with the extra damage only applying to the third attack.

I thought this was weird because the way i've always thought power attack was used is either all of your attacks for the round are power attacks or not. But the way it's worded I can see if it can be used in that way.

The second question I have is can you declare power attack on an attack of opportunity? Assuming you weren't declaring power attack in the previous round (or if you have combat reflexes and someone provokes from you at the beginning).

[JohnHawkins]

He is Wrong read the feat
Benefit: You can choose to take a –1 penalty on all melee attack rolls and combat maneuver checks to gain a +2 bonus on all melee damage rolls. This bonus to damage is increased by half (+50%) if you are making an attack with a two-handed weapon, a one handed weapon using two hands, or a primary natural weapon that adds 1-1/2 times your Strength modifier on damage rolls. This bonus to damage is halved (–50%) if you are making an attack with an off-hand weapon or secondary natural weapon.

When your base attack bonus reaches +4, and every 4 points thereafter, the penalty increases by –1 and the bonus to damage increases by +2.

You must choose to use this feat before making an attack roll, and its effects last until your next turn. The bonus damage does not apply to touch attacks or effects that do not deal hit point damage.

[Chess Pwn]

I'm pretty sure the answer is yes to both. Power attack is decided before an attack roll, but lasts the rest of the round once activated.

EDIT: I guess I can see it being before you make an attack roll in a round. I'm no longer pretty sure I'm correct. I'm down to, might be.

[Beopere]

Your friend is correct.

Power attack can be activated ANY time before an attack roll and lasts until your next turn. It can NEVER be turned off once activated.

You could take your turn without it, and use it during an attack of opportunity (and all future attacks until your turn).

Regarding the text John quoted:
You must choose to use this feat before making an attack roll, and its effects last until your next turn.

The important part here is you must choose before AN attack roll, not the FIRST attack roll.

[Ravingdork]

Your friend is correct. You can activate before an attack roll--any attack roll, be it an attack of opportunity or the first or last attack of your turn--however, you are stuck with the penalty until the start of your next turn.

[Dirkwolf]

Alright cool, that's sound logic there. Thanks guys =)

[Jiggy]

It's set up so that you can't:
A) Roll first, see that you rolled high, and then turn it on for "free" damage;
B) Turn it on for your first attack (highest bonus), and then turn it back off again to make your iterative more likely to hit.