House rules: The called shot.

In a lot of games I have ran, there is always a circumstance where a player would like to make a called shot at an enemy. Within the pathfinder rpg, and even DnD there are no rules or substantial charts for making a called shot against an enemy and what the results are. So my play group and I have devised a simple system that is both player and DM friendly. (Mind you this rule can have devastating effects on your monsters so use with caution.)

So, for starters you need to establish what it is the player is trying to strike that way you can decide the difficulty of the attack. Called shot should be incremented based on the size of the location being attacked, but before you do so you need to understand the difference in what is or isn't a called shot. To make a called shot first the player needs to specify the location on the enemy he/she wishes to attack. (Declaring you want to attack the left flank of a large creature such as a dragon is not a called shot, that is called an attack.) The area should be a very specific location such as between the ribs directly under the armpit of the enemy/creature, or the eye would be an acceptable declaration.

Now you as the DM need to decide just how difficult that specified location is to hit based on a few simple questions. How large is the area being attacked. To help out here is a simple chart based on size location.

Fine: (this is 6 inches or less) +8 added to the base Armor class to hit the area.
Diminutive: ( 7 inches to 1 ft) +4 added to the base Armor class to hit the area
Tiny: (1ft 1inches to 2-1/2ft) +2 added to the base Armor class to hit the area
Small**: (3ft to 5ft) +1 added to the base Armor class to hit the area
**(These area's should only be incorporated or approved by the DM if the creature is Huge or above)

Now that you have determined the difficulty of striking the area you need to decide if the are any additional factors to add to the difficulty before the attack is made, such as is the targeted area armored? if so the penalties for sundering armor should apply as normal. (an alternate option is to add an additional AC bonus to the targeted area based on what material the armor is made out of.)
Padded: +1/Leather/Hide/Studded: +2/ Metal: +3**
**(Special metals such as Adamantine should still apply their damage reduction rating if the area is struck.)

Now the attack is made against the targeted location. As the DM you need to determine if the called shot will be a fatal blow if the attack is landed. If the attack has the potential to kill the target if successful I have devised a ruling to determine wither or not the target survives the blow. If the attack is successful the target must make a fortitude save DC 10 +damage dealt or die. (as i said earlier this can be used to mow down monsters in single hits and forces the DM to run his villains with care, but remember DM's monsters can aim as well, and not all called shots are fatal.)

Alright, let me toss out an example so that this muddy water can clear up a bit.
"Crow the barbarian has engaged Thwak the Orc warlord in single combat! In the beginnings of the fight Thwak delivered some devastating blows to Crow and the outcome for our hero looks grim. Crow decides that he has to win this fight in one hit or be slain by the monstrous Orc. So Crow declares that he wants to make a called shot using his greatsword and cleave it into the throat of the mighty Orc. Thwak has an initial armor class of 20 but striking him in the throat is far more difficult than just striking him outright and the throat is a Fine Target increasing Thwaks armor class by an additional +8, making his adjusted AC 28, Thankfully for Crow the area is unarmored so no additional adjustments need to be made to strike the area. So Crow makes his attack. Crow is +14 to hit with his enchanted Greatsword and rolls a 16. (14+16 = 30) Crow lands a mighty cleave into the throat of Thwak. (Now obviously a greatsword to the throat has the potential to be fatal so this attack will force a fortitude save.) Crow's damage when wielding his greatsword is 2d6+8, so he rolls damage normally as he would with any attack. Crow deals 14 points of damage to the throat of Thwak and forces a fortitude save difficulty 10+ damage dealt so Thwak then needs to roll his fortitude save and come up with a total of 24 or above to survive the attack. Thwak has a +10 to his fortitude save but only rolls a 4 on his save, failing the check and getting his head removed as Crow shears his head from his shoulders."

This rule may take some time to become familiar with but has the potential to increase the flavor of your combat scenes by forcing your play group to do more than just roll dice and tell you damage. This rule can be utilized by any attack that requires an attack roll, even touch/ranged touch spells!
Enjoy.