What Are the Dominant Weapon/Armor Configurations?

For armors I'd say:

• Auto Phoenix
• Auto Protect
• Auto Haste
• See below

Auto phoenix for auto reviving your characters (this uses phoenix downs first, and if you're out, mega-phoenixes are used).
Auto protect for auto protect status (dispel can't even remove it).
Auto Haste for those extra turns before the enemy.

The 4th slot depends: Auto-Potion and X-Potions are a great combination. Some people use Ribbon.

For weapons i'd say:

• Break damage limit
• Evade and counter
• Magic counter
• Armor Piercing

Break damage limit and armor piercing for those basic attacks and limit breaks over 9999 damage.
Evade and counter for dodging physical attacks. Even if it fails, you still do the basic attack.
And Magic Counter for countering if you were struck by magic.

But then again, it depends on what you'll be fighting I guess.

If you are making a weapon and armor that is the "best" for dealing damage while surviving fights, there are a few things to consider first.

Weapon req. Break Damage Limit-so you can actually hit for 99,999 opt. Everything else-though here are some of the better choices. opt. First Strike-situational-for lower level enemies. opt. Counterattack/Evade and Counter/Magic Counter-VERY useful for bonus hits. opt. 1 MP cost/Mana Booster-great for casting or using abilities like Quick Hit opt. Triple AP/Triple Overdrive-Situational for farming AP, though Triple Overdrive is great as a standard damage dealer opt. Status/Elemental Strikes-1 shot KOs, but what for at this point?

The key for a winning piece of armor relies on knowing what you're fighting. If you're in Omega Ruins, you will need some confuse/stoneproof armor, as Malboros and Demon walls can end your game fast. Penance, Nemesis, Dark Aeons-require auto-abilites so that when you do die, you can recover instantly. Hard to kill your party with auto-life and reraise. NOTHING in the game requires Break-HP limit, though it is pretty to get to 99,999, and makes some fights easier. You can sub out Auto-Protect for this if you want, then add Ribbon as your 4th slot. Armor req. Auto-Haste-never lose your speed req. Auto-Phoenix-second chance, as long as someone is alive req/opt. Auto-Protect-halved damage always opt. Break-HP Limit-high HP numbers opt. Ribbon-status immunity opt. Proof skills-deathproof/stoneproof-but why not use Ribbon instead? opt. Auto-Shell, Auto-Regen-great for survivability

Personally, I go with Auto-Haste, Auto-Phoenix, Ribbon, Auto-Shell-and Break Damage, Triple Overdrive, 1 MP cost, Counterattack. You get super defenses, infinite haste and reraise, Overdrive spam and cheap quick attacks.

For armors, I used Break HP Limit, Auto-Haste, Ribbon, and Auto-Phoenix to kill Penance, and only Auto-Haste and Auto-Phoenix were really essential. Stone proof would suffice instead of ribbon, and BHL was more useful for farming Dark Yojimbo for a bunch of Dark Matters/BHL+Ribbon armors than it was for the final battle.

As for the best weapons? It's the Celestial ones, no argument. Yeah, some of their abilities are kind of mediocre, and after you max the Sphere Grid the Double AP ability on some of them is just insulting. And yes, they do have funky damage calculations, which you might care about when farming Earth Eater for fortune spheres, but none of that matters. The Celestial Weapons all have a hidden property that cannot be duplicated via synthesis, it ignores the defense stat of the target (except when used for limit breaks, which is fine because Quick Hit).

Someone tested it and posted their results here.