Plane Sailing said:
* In one campaign we just don't have cleaves off AoO. I think that we've discussed an option (which I particularly think a decent one) is that if an AoO drops a foe and you have cleave, then it counts as if you haven't used that AoO - you get to cleave into a different AoO, but you can't use the cleave attack against someone who hasn't provoked an AoO
Having Cleave give you free AoO only partially fixes the problem I saw when the big butch fighter got attacked by many Tiny Constructs.
In your option, he would drop the first one that attacked then cleave/free AoO the 2nd one, then use up his Combat Reflexes AoOs on the next 2 or 3.
Or do you imply that Great Cleave would give unlimited 'free AoOs', which has exactly the same effect, in this instance, as allowing Great Cleaves on AoOs.
When this came up in game there was a unanimous agreement to disallow Cleaving on AoOs and I have seen/heard no discussion that offers me a better option.
Also, the vision I have for Cleaving is: warrior takes a mighty swing, cuts clean through his foe then cuts into the next foe along. Great Cleave means that the swing is so mighty that it can cut into a third foe if the second is dropped. I realise that this doesn't fully work for piercing weapons.
Given that an AoO is a reaction and, therefore, not a considered attack, I don;t see it as reasonable that the blow should be able to go through into the next foe.
In fact, I can see an argument for not including STR bonus to damage on AoOs, but I'm not going to advocate that - too much for players (and me) to remember.
I can also see an argument for limiting cleaves to adjacent foes - something to think about later, perhaps.