I have thought about that topic and went through the opinions above.
First Question: Are called shots appropriate?
We already had a thread about called shots, mostly to say they were useless (given that you really can't aim in combat, you strike where you can).
I think, this is not the case, for...
1st. What about missile weapons, you could say I can cover that with Sniping (alternate Ambush syle) but you can aim, even when somebody is aware of you.
2nd. In certain situations you might need a called shot (see zombie example above). I think its unappropriate to adjust the normal crits to the location, for the damage increase with the location should be reflected in the damage effects i.e. in the example above the (movie)zombie should be dead pretty fast after being hit in the head as Smaug should die after a arrow hits into his heart.
So
imo called shots are appropriate.
Second Question: What rule simulates called shots best?
The above mentioned methods include adding tables, altering the description, specialized mechanics to alter the number of the crit result and taking the critical level as success threshold.
Skiming through that, I think that taking the critical as a damage thrreshold is the best method but not in the presented fashion. Justins version of the rule implies, that that you assign the location a difficulty rating based on on the crit level. The highest crit we have is E (in Arms Law). If I can hit a heart with a E critical I will try that every time, for with a damaged heart a foe is practicaly deafeated. So no way here.
Now my attemt: Assign a OB modifier to every specific critcal and let the player (heavily assisted and restricted by the GM) choose one critical, that he likes to achieve. If he reaches the crit threshold (class of the specific crit A,B,C,D or E), he has done that hit, if not normal result applies.
Pros:
-no extra tables needed.
-no big new rules effort for players, just looking up in the existing (updated) tables for the GM.
-damage-location ratio.
Cons:
-PCs could missuse positive mod on low crits to hit hard to hit opponents.
-Much work and balance issues for the GM til he figured out the fitting mods for the crits.
-PCs normally don't state a specific result when they wish to hit the thing in the head.
Even with these cons, this is the best solution for me. The first contra point could be invalidated by not assigning positive mods to weaker crits. The second stands valid, so one just has to decide, if its worth the work. The third can be overcome by GM guidiance or choice (i.e. the GM chooses the specific crit and tells the player just the mod. for it).
comments welcome
Ben