Here’s a new system I used for combat today.
Rather than having one character roll to hit a static AC, I had both sides roll off—one to attack, one to defend.
The Base Attack Bonus is now called the Combat Bonus.
To attack, you roll d20 + Combat Bonus + Strength/Dexterity modifier + Weapon Bonus (if any).
To defend, you roll d20 + Combat Bonus + Armor Bonus + Dexterity modifier.
The player with the higher roll wins.
It will probably go smoother if you combine the numbers and create an Attack Bonus and a Defense Bonus.
For instance, Shawn the Neurobarbarian has a Combat Bonus of +2, a Strength modifier of +3, and a +1 sword. That gives him an Attack Bonus of +6.
(In my game, Strength could be used for Melee weapons and Dexterity could be used for Ranged or Light Weapons—see previous post to understand weapons and armor.)
He wears Heavy Armor (+7), a Dexterity modifier of +2, and adding his Combat Bonus gives him a Defense Bonus of +11.
This system benefits the defender, but I like that. The randomness prevents several things that I don’t like: first, there is no static AC that players can eventually guess. Also, it means that every missed attack is not just a brief statistical ‘whiff’, but an engaging moment at the table, with a lot of uncertainty.
If an enemy is flanked or otherwise distracted, they lose their Combat Bonus to defense—the Armor Bonus still applies, as does Dexterity.
From the playtest, it was a little clunky at first (we had a totally new player and the system was unfamiliar) but once they got the hang of it things seemed to run pretty smoothly (or smooth enough, given that it was a hyper-buggy Google+ connection).
Anyways, hope people find this useful. I thought it added a lot!