Figuring out the combat system for my fantasy heartbreaker turned out to be pretty easy compared to nailing down the particulars of the weapons and armor that characters will use in it. I want different types of weapons to have meaningful differences, but I don't want huge complicated tables with lots of messy modifiers to look up or remember. After a lot of false starts, I'm tentatively happy with what I have now.
Armor comes in three types: Light, medium, and heavy, giving a base AC of 12, 14, or 16, respectively. Light armor includes light, non-metallic, and relatively flexible options such as leather and padded armor. Medium armors are made of metal or other hard material, but in flexible forms such as mail, scale, brigandine, and such. Heavy armors are made of large rigid plates of metal or some other hard material. The exact type of armor a character gets in any of the three classes is determined by the player and GM, and has no further game mechanical effect.
Shields increase AC by 1, as usual. I'm considering making a shield a requirement to use the character's Combat Rating defensively, too.
Weapons come in broad categories: Axe, Blade, Bludgeon, and Stick, and further divided into light, medium, and heavy types.
Axes are chopping weapons which are good at breaking through armor, and so receive a +1 bonus to combat rolls. Damage is 4/6/8 for light, medium, and heavy types, respectively. Examples include the hand axe and tomahawk (light), battle axe (medium), and polearms* (heavy.) All axes use the wielder's Might modifier.
Blades are slashing and slicing weapons. They are among the hardest to master, but have the highest damage potential at 6/8/10. Examples include daggers and short swords (light), all of the various "normal" swords (medium), and great swords such as the bastard sword and two-handed sword (heavy.) Light and medium blades use the wielder's Agility modifier. Heavy blades use Might.
Bludgeons are blunt, smashing weapons. They are the easiest weapons to wield, and also good at delivering impact damage through armor, and so receive +2 to combat rolls, but also have the lowest damage potential at 3/4/6. Examples include the club/cudgel/shillelagh (light,) the mace and war hammer (medium), and the maul (heavy.) All bludgeons use the wielder's Might modifier.
Stick weapons are long, slender weapons used mainly for thrusting maneuvers. They gain a +2 bonus to Interpose actions. Damage is 4/6/8. Examples include the quarterstaff (light), the spear (medium), polearms* and lances (heavy.) All stick weapons use the wielder's Agility modifier.
*Since polearms typically feature both heavy chopping blades and spear points or spikes, they may be used as either axes or stick weapons, whichever is most advantageous to the wielder.
Most light and medium weapons (except the quarterstaff) may be wielded with one hand, and combined with a shield if desired. Most heavy weapons (except the lance from horseback) must be wielded two-handed.
Missile weapons are another can of worms with which I'm still grappling...