I'm looking to make house rules on Attacks of opportunity, particularly to favor those clever enough to utilize combat reflexes.
Instances I think should or might provoke attacks of Opportunity, but correct me if I'm wrong by the rules or out of reason:
1. Doing any standard action within a threatened square that doesn't specifically say "doesn't provoke an attack of opportunity"- feel free to provide more, or specific, exceptions
2. Charging at an opponent (moving more than double your movement rate, or moving your double movement rate into a threatened square- and not attacking), especially if they ready an action or are fighting defensively or take a full-defense action.
3. Making a critical miss/fumble.
4. Becoming Prone- assuming the attacker who gets the attack of opportunit either has Combat Reflexes or hasn't used all of their attacks in the round.
5. Getting up from Prone (unless you make a 5 ft adjustment first? or would that provoke an AoO? -speaking of which, how the hell does the 5 ft adjustment rule work, especially when applying to moving in or out of a threatened square?! There has been some debate on this with my players.)
6. Not withdrawing, but moving out of a threatened square. (5 ft Adjustment?!)
7. Moving through a threatened square. (Charging especially, straight line, yes, but what else?)
8. similar to 2- if attacking someone with a readied action or combat reflexes that is fighting defensively or using the full-defense action. (EDIT: Actually this would be # 2, wouldn't it?)
9. Healing another while in a threatened square, or performing any spell other than an instantaneous/free action spell while in a threatened square.
10. If the opponent attempts to grapple =AoO, fails to grapple AoO. (Modify it to include an opposed grapple check, perhaps only if the person has Improved Unarmed Strike and/or Improved Grapple and/or Combat Reflexes, etc...if they fail, allowing a grapple of opportunity if someone enters your threatened square and critically misses- especially if charging or attempting a bullrush. Basically I envision the trip/flip/throw using an opponent's momentum against them sort of situation.)
Combat Reflexes: Obviously- additional attacks equal to their dex mod...
If character has Dodge, they can sidestep a charging opponent AND get an attack of opportunity if their dex mod allows.
Similar to the modifications suggested in #10. if opponent is in a threatened square- and fails a touch attack, an attack of opportunity may be made, which includes a grapple attempt since the touch attack/grapple attempt brings the opponent within reach of such an attempt.
Any reason to include attacks of opportunity to apply to range attacks, provided there is a readied action, casting defensively, fighting defensively, combat reflexes or otherwise?
Also, suggestions rules on Parrying, deflectiong blows- which might be followed by an attack of opportunity or a cause for an opponent to lose their dex bonus would be nice.
So far, the only time that I actually was able to really utilize combat reflexes was when my character was attacked by stirges and obviously them trying to suck my blood out provoked attacks of opportunity- and equal to my dex mod I might add.
I admit to be hazy on the exact situations and rules involving AoO's, so I want to hear what works for people in their games before I declare any house rules on the matter, especially at the risk of overpowering existing feats.
As you state, many (if not all) of the actions you mention do provoke Attacks of Opportunity per SRD; I'm sure others with more time will be able to elaborate in detail.
My two cents on the subject are that I think it is in your best interest to master the AoO RAW as they are paramount to the 3.X rule set. I think you'll find that even knowing what actions provoke and which ones do not does not necessarily result in more AoO being taken. My gaming group and many intelligent monsters take great pains to not allow the enemy to get any more attacks on them if possible.
AYBABTU. Make your time.
Addressing your list of points/concerns:
1. PHB, page 141. There's a list of actions sorted by type (Standard, Move, Full-Round, Free, Nonaction, and varying action), which states whether they do, don't, or sometimes provoke. Those that sometimes provoke generally have explanations as to when they do and when they don't.
2, 6, and 7. Movement provokes an attack of opportunity anytime you leave a space threatened by an enemy. You can avoid this under certain circumstances -- the first and last squares of movement don't provoke when you Withdraw, and a successful tumble check keeps you from provoking -- but those (and any other means of negating the AoO) are exceptions and thus specifically stated. Thus, regarding point #2, you provoke an attack of opportunity if you charge an opponent whose reach exceeds yours (because you will have to leave a space he threatens to reach him) or one who has the feat Hold the Line (which allows an opponent to make an AoO against a charging opponent (and only a charging opponent) when they enter a square the character threatens -- an exception which, again, is specifically noted in the feat description)
Note: There's a difference between Readying an Action and Taking an AoO. The former allows you to take your combat actions in reaction to a predetermined event, even in the middle of someone else's action (say, you fire your crossbow at the first enemy creature who ceases to be engaged in melee), while the latter is basically reaching out and smacking somebody on the fly because they left themselves open.
3. I don't know if the RAW supports this, as I'm honestly not sure if the RAW supports critical fumbles in this edition. We've almost always played this way as a house rule. Just be wary, lest you or an NPC charge at an opponent, roll three natural ones, and stab yourself in the eye with a greatclub.
4 and 5. Becoming prone (whether by flinging yourself to the ground or by being tripped) doesn't provoke an attack of opportunity - -you're moving too fast, it's a free action. Rising from prone, however, does. We've always allowed a "five foot scamper" while prone to try and rise, but we've often had difficulties with wolves.
Regarding the five foot step: it doesn't seem, to me, to strain credibility to assume that a character who can typically move twenty to thirty feet in a matter of 3-5 seconds (most PCs, even when armored) could make a five foot adjustment to their position even with relative haste and still take care not to leave any openings in their guard as they do so.
8. If someone has readied their action to attack the first person who attacks them, the readied action is resolved either before or simultaneously with your attack. I forget which. They can't do this while taking total defense, but can while fighting defensively. Fighting defensively does not really lend itself to taking AoOs, though, as you take a -4 penalty on attack rolls and gain no new means of threatening your enemies.
9. Casting any spell, be it Cure Light Wounds, Magic Missile, or Wish, provokes an attack of opportunity unless you make a concentration check to cast defensively. Failing the check results in the loss of the spell. I don't know of any explicit statement that casting a quickened spell (or one with a casting time of "1 Swift Action") doesn't provoke.
10. When a character without Improved Grapple or Improved Grab attempts to initiate a grapple, they provoke an AoO. Success on this attack causes the grapple to fail automatically. You can take actions other than attacks on Attacks of Opportunity -- for example, two characters with Combat Reflexes and Dex Modifiers of +4 can get into a sundering competition and each attempt to sunder the other's weapon five times in one round. There was an article on WoTC about that, I think, but I don't recall where. The rule is, I think, that you can only take Attack Actions, not generic standard actions. You can Sunder, Trip, or Grapple (I think), and maybe even bullrush, but no Spell of Opportunity for you.
That's all I've really got time for (cursed work, keeping me away from what's really important,) except that I think there's already a feat somewhere entitled "Sidestep Charge". Can't for the life of me recall where, though.
3. I don't know if the RAW supports this, as I'm honestly not sure if the RAW supports critical fumbles in this edition. We've almost always played this way as a house rule. Just be wary, lest you or an NPC charge at an opponent, roll three natural ones, and stab yourself in the eye with a greatclub.
By the RAW, a natural 1 is simply a miss. However, page 28 of the DMG lists the variant Critical Misses (Fumbles). By these rules, rolling a 1 causes a Dexterity check (DC 10). Failure causes something bad, per the DM's ruling. I generally go by rolling the attack again instead of a Dexterity check, and causing Attacks of Opportunity on a failed check (though I'm never sure quite what to do with ranged attacks - I don't want to penalize other PCs for one PC's folly...).
And just remember , Drawing a weapon does not provoke ( Despite the fact i played it this way for something like 5 years)
Logos
I could swear it did in 3.0, because I remember going by that rule for a long time.
(though I'm never sure quite what to do with ranged attacks - I don't want to penalize other PCs for one PC's folly...).
Snapped bowstring or jammed crossbow trigger. Or you shot yourself in the foot while trying to wind the damn thing.
My group plays with a critical miss variant rule--if you roll a 1, roll again, then if you miss the target's AC by more than 5 you are off balance, drawing an attack of opportunity and lose your next attack (if you have multiple attacks per round). If you miss by more than 10, we go to a fumble chart, with options of dropped weapon, falling prone, damage to weapon, damage to self, attack targets ally accidentally (requires attack roll to hit), weapon becomes wedged in opponent's shield or a nearby object. If the situation makes the result on the fumble chart impossible, such as accidentally targeting an ally with a melee weapon when there's no ally in range, you just go off balance. Having to make a second attack roll means a high level fighter is unlikely to critically fumble (which seems reasonable) while a 1st level character is.
Aside from the house rule possible outcome of critical miss outlined above, I think the rules are pretty thorough about attacks of opportunity (and pretty complicated), and you're better off mastering the existing RAW before you mess with making more house rules on it.
On movement: Whenever a character exits a threatened square, he provokes an attack of opportunity.
If the character does nothing except move (not meaning taking move actions here.. only actual movement from one square to another) in one round, and is not running (moving faster than two move actions), then the first and last square he passes out of do not provoke attacks of opportunity from movement.
5-foot steps are a special free action that can be done once per round when the character has made no other movement (though he can have taken move actions, such as drawing a weapon). They do not provoke attacks of opportunity, but a character cannot take a 5-foot step through difficult terrain (if it would cost him 2 or more squares to exit the square he is currently in).
Aside from the house rule possible outcome of critical miss outlined above, I think the rules are pretty thorough about attacks of opportunity (and pretty complicated), and you're better off mastering the existing RAW before you mess with making more house rules on it.
I do think this is how I'm going to go, with the RAW and with the critical fumble rule- unless my players gripe too much.
But as far as I'm concerned about REALISTIC combat scenarios, for instance each move can and will take 3 seconds for instance- or at least all movement and attacks and so forth can be accomplished within 1 minute...and so can entire combat, then if someone critically misses- and in my game you don't have to reroll to see if you put your weapon through your face or not, dm determines, with possible usage of the hit location die- then they are opening themselves up to attack, they might not be denied their dex bonus or otherwise count as flatfooted, but they're definitely putting themselves at risk- so an attack of opportunity, ESPECIALLY if it comes from an attacker with combat reflexes, makes sense to me.
And as far as unarmed combat goes, I'm tempted to include critical misses and my idea of AoO grapple attempts. Maybe not AoO grapple attempts for armed opponents or necessarily unarmed opponents on armed opponents, but yes, AoO's and Critical Fumbles for unarmed opponents, perhaps an AoO armed attempt to grapple, but that might only occur on either a critical fumble or when the opponent is denied their dex bonus (or ac decreases by 2, when charging).
But again, these are just things I am considering and so far the only thing the board seems to be open to is critical fumble AoO's. bending the rules otherwise would seem...a bit of a push.