ODnD Hack: Combat Styles

As has been mentioned, SEPTIMUS is my long range very nebulous homebrew system. Of more concrete interest however is creating an OD&D hack of my own. So, from time to time I will present sub-systems that can be plugged into pretty much any version of OD&D or its retro-grognardian clones. Here is one for combat styles.

Always-On Benefits: This is a benefit that you derive all the time.
Encounter Benefits: You may use one benefit per encounter. After resting for a turn, you can use this benefit again. Additionally, if they are being used, you may spend a FATE point to use a benefit again this encounter. At the DM's discretion, fighting men may gain an additional "per encounter" usage of a fighting style at level 4 ("HERO") and/or 8 ("SUPER HERO").

These are intended to be used with a relatively simple weapons system like that presented in the LBB.

ONE HANDED WEAPON ALONE - Usable by anyone
Wielding a one-handed weapon alone is the preferred style of the duelist. Most prefer to opt for something that puts that second hand to work, but there are times when the flexibility of using just a trusty long sword or mace is helpful. It also helps one to exploit an opening given by an opponent.
Always On: Your off-hand is available for other items such as a lantern, potion, climbing, or treasure.
Encounter: If you miss with an Opportunity Attack or attack against a fleeing combatant, you may immediately reroll the attack and deal maximum damage if you hit.

TWO HANDED WEAPON - Usable by anyone, weapons selection permitting (mages likely limited to staves)
Polearms and other large weapons are popular for a reason -- they work.
Always On: Gain either Reach or +2 damage (or use a D10 for damage dice instead of D6). Reach allows first strike vs. foes without Reach (regardless of the initiative roll) and may allow the weapon to be used from the second rank.
Encounter: Instead of rolling damage, consider the damage from this blow to be maximized.

ONE HANDED WEAPON + SHIELD - Usable by fighting men and clerics
The sword and shield is a classic staple of both reality and the literature, and any warrior is safe to select a shield.
Always On: Gain +15% bonus to your AC and to saving throws when parrying. If using a large shield, share this benefit with an adjacenet ally.
Encounter: Reduce the damage done to you by an attack to zero.

DUAL WIELDING - Usable by fighting men
Multiple blades flashing is the hallmark of many dexterous fighters who favor an accurate offense over defense.
Always On: If you hit, roll damage twice and take the best roll.
Encounter: If you miss with an attack, you may immediately reroll the attack.

Special Cases:
Archery counts as DUAL WIELDING because it can use "volley fire."
Crossbows count as TWO HANDED WEAPONS because they deal grievous wounds when they actually hit.
Slings count as ONE HANDED WEAPONS, except the reroll may be used against a LARGE target because even Goliath can be humbled by a simple sling.
Hurled weapons vary: Darts are like dual-wielding due to their high rate of fire. Javelins can easily be used with a shield. Pilums (two handed javelins) are like two handed weapons.

IS IT BALANCED?

Originally, shields give effectively a -5% chance to be hit. Over the course of a 10 round fight, that's about one fewer hits every fight (assuming a fighting man type is taking two attacks per round). So, allowing a shield user to just outright negate one hit per encounter is legit. It also makes the parry manuever viable and lets them shield a friend, potentially.

Dual wielding basically grants +1 damage all the time, makes your damage more reliable, and decreases the chance to miss significantly one time per encounter. This balances nicely against two handed weapons, which also boost offense but in a "swingier" manner; the average damage is higher (+2 vs. +1) but it is less reliable. Two handed weapons are more likely to kill someone outright, but dual wielding is more reliable. A reach weapon does less damage than either but has signifiant advantages of first strike, which might kill a foe outright before they even get a chance to attack you, as well as the potential to be used from the second rank.

One handed weapons are available to anyone, which is a plus. You also get some versatility. The Encounter power is slightly more potent than the dual wielding one, but more situational as well. It nicely reflects the danger of letting down your guard around a duelist, and it makes the opportunity attacks of wizards actually matter (at least once per fight).