Probably OGL Ancients. The systems are just terrible. They tried to make combat more 'realistic' by including some rules for armor that was incredibly clunky. If I recall correctly:
The attack makes his roll. The defender makes an opposed defense roll with his shield. If it gets through, the defender makes a defense roll to see if he can dodge the blow. If that hits, the defender makes a defense roll to see if he can twist to put his armor in the way of the blow.
One attack roll, three defense rolls. ???
I have shelves and shelves of books I don't use, but only that particular book has drawn my ire. Unreasonable? Probably.