My game uses the Grim and Gritty rules.
We added a called shot to the table that lets you make an attack, but only aginst a Flatfooted opponent, as a standard action, at a -6 penalty, -10 with a lethal damage weapon, that provokes an attack of opportunity, though that usually doesn't matter as you normally can't AoO while flatfooted, which forces the wounded party to make a Fort save DC 10+damage dealt or be rendered unconscious for X time.
We've used it a few times and it worked just fine, because there's no sneak attack damage being added, and people's helmets give them a little DR. Having played the Thief series (R.I.P. Looking Glass Studios), being able to blackjack opponents is just DAMN cool. Plus, you basicially only get one chance to do this, as you can't do it while flanking or anything. Makes feinting in combat more useful again. Doubt this is terribly useful, but I thought I'd share regardless.
I like the idea of 1 point of damage from each damage die being Subdual. That'd give GnG characters a lot more, um, survivability. It'd take Crits down a notch, too, as in GnG you only add bonus damage once, so your 1d8+3 (1 sub) would become 3d8+3 (3 sub). You'd take leathal damage off first, in the dcase of DR, so it would mean that a lot of hits might only deal subdual damage. Cool idea. I'll have to throw this one at my GM, though, it'll make me have to remake my character sheet AGAIN!!
- Kemrain the Unofficial Grim and Gritty Spokesbeing.
On a side note, would "Unofficial Grim and Gritty Spokesbeing" fit under my nickname if I became a community supporter?