In thinking further about Special Maneuvers, it occurs to me that they a probably too powerful. I think perhaps the victim should get a Saving Throw. So it would work like this:
If the Combat Roll is 15+, the attacker has the option to make a Special Maneuver. If so, he subtracts 5 from the Combat Roll so that he does less damage (so a roll of 17 reduced to 12 has a base damage of 2 now). He can reduce the Combat Roll to 10, in which case he does no damage other than the results of the Special Maneuver. These Maneuvers include:
Wound - the opponent must make a CON Throw or roll on the Wounds Table (which usually happens only if reduced to 0 or less HP).
Knock Down/Back - the foe must make a DEX Throw or stumble back a few feet or falls down.
Disarm - the foe must make a DEX Throw or his weapon goes flying out of his hand.
Stunning Flurry - a flurry of disorienting blows that forces the foe to make an INT Throw or lose his next turn.
Deadly Display - the character's display of martial prowess is so intimidating that the foe must immediately make a Morale Throw.
The Referee should feel free to add any other Special Maneuvers that seem fun.