Hit Locations and Called Shot Criticals

Keith J Davies 

.... hit locations instead of straight random multiplier for damage, and armor coverage

Matt Miller

Hit locations are always a tempting location, but it certainly adds complexity. You roll to hit, roll for hit location, then roll for damage. It adds a fair bit of complexity, because different locations then have different armor values. The bad ones go like this: Attack, Roll for Location, Lookup Location, Lookup AC, Roll for Hit, Roll for damage, Add damage multiplers.

The Skill and Powers 'Called Shot Criticals' did it better, where you chose a location, with harder to hit locations getting a penalty to attack. Then you rolled severity, (based on weapon size) and then got a damage multiplier, and some extra effects. For example, a called shot critical to the head was at -8, but a severity of 10 could mean instant death. Rob ran a campaign where villains kept forgetting their helmets, so a character if AC -5 had a head with an AC 10 (effective AC 2), meaning several significant enemies were one-shotted by being beheaded. It was glorious!...One of the things that people really like is being able to say "I am a cut at his head". Yet the CSC penalty to hit made sure it wasn't something you wanted to do all the time

In fairness, they were supposed to fail a saving throw vs. death as defense against a critical, but we frequently neglected that rule, because it was so much fun. Were it mine to design again, I'd do it like this: Choose a location, with different locations getting a bonus to AC. And then different locations have a different damage dice, damage multiplier, or bonus damage attached.

Keith J Davies 

DnD 3e also had percentage checks for things where character ability and circumstance (mostly) didn't change things. For instance, miss chance due to concealment (20%/50%... unless you had a feat or something that changed it; BAB and high ability scores didn't improve it). Still almost always in steps of 5%, but the percentile roll meant you don't add modifiers.

Matt Miller

The cover/concealment thing was weird, but I think they included that for reasons of spells. A +10 to AC is not the same as a 50% miss chance, which stacks with AC and makes it harder. The sequential filter is nice, as it makes concealment hurt both the characters with low and high BAB equally

Keith J Davies 

I'd say the two rules interact, rather than 'stack'.... If they stacked, though, it should be 0% chance to hit.... The net effect is similar (decreased chance of being hit), but it's not the same thing (there are attacks that ignore AC but not concealment...)