Here's the rules that I've been using in my campaign for weapons and armor. (The "base system" is White Box: FMAG with ascending armor class.)
Armor Class Values
Base unarmored AC: 9
Buff Coat / Furs: 11 AC
Chainmail: 13 AC
Brigandine: 14 AC
Plate: 16 AC
Shield: +2 AC
Helmet: +1 AC
Greathelm: like a regular helmet, but also protects you against critical hits (i.e., roll damage as if it were a normal attack instead of a crit)
The maximum Armor Class that a character can have is 18.
Weapon damage is mainly based on your class.
Wizards, thieves and clerics deal d6 damage with most regular weapons. Wizards and thieves can use any kind of (non-magical) weapon that they want (including halberds and greatswords) but it's only going to deal d6 damage since they can't really "use the weapon to its full potential". Most magic swords will refuse to be wielded by the unskilled.
Fighters deal d8 damage with most weapons (axes, maces, spears, swords, etc...). The notable exceptions are daggers, which are limited to d6 damage, and big weapons like zweihänders or bec de corbins, which roll a d8 for damage, but if you roll a 1 it turns into an 8. In other words, if you hit with a zweihänder, there's a 2-in-8 chance of dealing 8 damage, and you'll always deal at least 2 damage.
Bows and crossbows roll d6 for damage, no matter what your class is.
Improvised weapons like broken bottles, pitchforks, shovels, etc... deal either d4 or d6 damage, decided by a coin flip or on a case-by-case basis depending on the type of weapon and who's using it.
Fighters that wish to dual-wield receive a +1 to their melee attack bonus, but their damage roll is unmodified (so, if you fight with 2 swords you still roll 1d8 for damage).