These are three rules I have used, off and on, for 30 years, give or take, without ever adding them to The List.
Great Blow: A fighter (including barbarians, noblemen, paladins, rangers, and men-at-arms) may strike a Great Blow. This is a mighty swing/thrust/etc. meant to inflict maximum damage. A Great Blow must be announced before rolling to hit and it adds +1 to effective initiative; if successful the attack does maximum weapon damage.
The target may negate the attack (i.e., avoid it altogether) by simply stepping back 3'; this can be announced after the to hit roll.
Full Defense: In combat it is assumed that fighters are taking risks while attempting to land their own blow. A fighter (including barbarians, noblemen, paladins, rangers, and men-at-arms) may fight in a purely defensive manner. This must be announced before initiative is rolled. A fighter in Full Defense cannot attack (including grappling or overbearing, missile weapons, use of magic items, etc.) during that round but gain +1 to A.C. for every two levels of experience (rounded up). This bonus only affects melee attacks.
Sir Roland realizes that the assassin has a poisoned dagger! Knowing that his retainers will arrive in just another minute and cause the cowardly thug to flee, he switches to Full Defense; as a 7th level nobleman his A.C. improves by +4.
Desperate Defense: Non-fighters, lacking the great skill of fighters, take many fewer risks in combat. But they, too, can strive to avoid being struck by mounting a
Desperate Defense: This must be announced before initiative. A character in Desperate Defense cannot attack, cast a spell, use an items, search for traps, etc., they may only fend off melee attacks. Such characters receive a +1 to their A.C. for every 4 levels, round up.
Willimar had no idea where the hobgoblin had come from, but he knew he was in trouble. Already hurt from the shaman's bolt of fire and separated from his friends he knew began to flail his staff around with no thought but fending off the creature's falchion. Willimar, a 7th level mage, receives a +2 bonus to A.C.