One of the interesting rules in one of the old Rolemaster Companions (I can’t remember which, possibly No. III), was the idea of a “wraparound attack”. You see, attack rolls “maxed out” at 150 over the opponents defense bonus. For example, if your opponent had a Defense Bonus (DB) of 40 and you rolled a 240, you were capped at 150 for your attack roll, even though you rolled 200 over his DB. That’s normally as far as the chart went.
Let’s say, though, you open-ended your attack roll multiple times, and ended up with a 310 to their 40, or some 270 above their level, normally you’d still be capped at 150, meaning 120 of that roll would go to waste. Under the optional rule, though, that 120 can be used for a second attack. If the remainder above 150 is also a hit, you get to roll that critical on the chart as well.
It’s a fun rule, and allows for grievous hits to do both a D-level and an A-level critical, for example. Even if you miss on one critical hit roll, you still have another waiting in the wings. The highest attack roll I ever saw using this method in a Rolemaster game ended up doing 3 separate criticals!
It wouldn’t come up often in D&D and its cousin (unless you’re using a d30 rule), but if you did cap damage at 15-20 above someone’s Armor Class, would it work to allow any remainder on the roll to be used as another potential attack? If it beats the AC, it can also be used to roll damage as well.
I think this rule works much better in games such as HARP or Rolemaster, though. I just don’t seeing it happening as often in games without open-ended attack roles. Games with open-ended rolls play to the sense of variety and uncertainty, and this rule definitely fits in with that mindset.