From Wizards message boards where you also posted this question.
From Jachyra- This has already been discussed, I'm sure, but I'll post this anyway.Say a guard has been walking a set patrol path over and over. You've studied him, and he's walked past multiple times. YOu want to take him out with one shot from your bow, a head shot maybe. How would you adjust your attack role? or would you?
From Arturick- Okay, YOUR CHARACTER that you made and have adventured with for quite some time is guarding the party's camp, and has been for a few hours now. A very well hidden orc with a crossbow has been watching you, and wants to take you out with one shot. A head shot,perhaps. Oh, and he's got a potion of True Strike, so he isn't going to miss.
The whole party gets killed in their sleep, ending the adventure and leaving a really bad taste in everyone's mouth. The DM says that some guy on the internet said it should work that way.
I'm sorry, what was your question?
If you want hit locations, damage specifics, HP per locations look at (these are all from memory 10+ years ago)Phoenix Command, Swords and Sorcery (Or Swords and Spells, something like that), I think Twilight 2000 has crit charts too but those won't work so well for D&D. I think the Swords and Sorcery had just about everything you'd ever want. Charts for weapon types vs body types.
Such charts got my mages hand cut off by a party members fumble and in a different game a character killed by critical gunshots (throat/trachea, wrist, and the real killer Eye/Partial Brain. -540 HPs).