Honestly, I have no idea if this is legal. I stumbled on the idea a while back and it seemed OK, but now I'm not sure.
I have a Monk that now has Snake Fang. He had Paired Opportunists already.
I'm planning on him eventually taking levels of Hunter and having an ape AC.
Snake Fang would allow my character to make an unarmed strike AoO when missed by a melee attack.
Paired Opportunists would allow his AC to also make an AoO, but I believe it would also need to be an unarmed strike.
Is this PFS legal?
Ok, let me get into some of the finer points of my question.
Snake Fang allows my character to make an AoO when he is missed by a melee attack. This attack must be an unarmed strike.
Paired Opportunists allows an adjacent ally with this feat to take an AoO whenever his partner gets an AoO.
1. In this scenario, does the ally's AoO need to be an unarmed strike also, or could the AoO be done with some other weapon?
2. If the AoO needs to be done with an unarmed strike, can the unarmed strike be used to make a combat maneuver like a trip?
3. Also, if the AoO needs to be an unarmed strike, could an ape animal companion make an unarmed strike? Would the AC need to take the Improved Unarmed Strike feat? Can an animal companion take the Improved Unarmed Strike feat? I know an animal companion with an intelligence of 3 can take a wider variety of feats, but I've read that weapon proficiency feats are not allowed. If weapon proficiency feats are not allowed, where does IUS fall? It's like a weapon proficiency feat, but not quite.
I would appreciate any feedback on this that people can think of.
It seems like you are really overthinking this. Snake Fang says your AoO must be an unarmed strike, it does not say anything about anyone else's AoO's.
Your AC doesn't need IUS because it already has natural attacks. These two things don't really combine/synergize/interact unless you're a Monk and then it gets all weird and convoluted. Luckily, your AC is not a Monk so that's all moot.
You can do any action that is a single attack action as part of an AoO unless you want to trip someone who has provoked the AoO by standing up from prone. The "trip loop" is expressly disallowed even though the rules seem like they might allow it.
You can do any action that is a single attack action as part of an AoO
Even vital strike?
FAQ: Can Vital Strike be used with Spring Attack? Can Vital Strike be used on a charge?
No. Vital Strike can only be used as part of an attack action, which is a specific kind of standard action. Spring Attack is a special kind of full-round action that includes the ability to make one melee attack, not one attack action. Charging uses similar language and can also not be used in combination with Vital Strike.
I suppose my language is not the clearest since I'm not even able to keep the difference between the two straight in my own head half the time due to Paizo's language lacking a certain clarity of its own. The FAQ's do seem to indicate that Vital Strike can't be combined with much at all. Sorry if I caused any confusion with my mixing of terminology. I wanted make sure I didn't accidentally green light a trip loop but instead I accidentally opened the door to Vital Strike shenanigans.
Added: my rule of thumb for Vital Strike is that it's a no go if I wasn't going to have more than one attack in the first place i.e. I have to be actually sacrificing an something to earn the extra damage. It hasn't let down yet but I'm a late adopter having only switched from 3.5 not long ago--part of the reason for my terminology confusion.