Quote Originally Posted by masamune1600
A number of materia (beyond the Master set) sell for 1 gil, even when mastered. These include all Summon materia. These materia can accrue enormous amounts of AP, so a direct gil to AP statement is clearly inaccurate.
m16 beat me to it. Arr!
W-Item, W-Spell, W-Summon, E.Skill, 2x Cut, Morph I believe, Slash All, Mime, MP/HP Absorbs, Steal As Well, Magic Counter, Final Attack, Quadra Magic, Sneak Attack, Gil Plus, Exp. Plus, HP <-> MP, Mega ALL, Underwater, Exit, Comet, Fullcure, Contain, Ultima

Apocalypse, Ragnarok, Ultima Weapon, God's Hand, Premium Heart, Missing Score, Conformer, Limited Moon, Death Penalty, HP Shout, Venus Gospel, Ziedrich, Chocobracelet, Poison Ring, Peace Ring, Champion Belt, Ribbon, Water Ring, HypnoCrown, Safety Bit, Reflect Ring, Tetra Elemental, Sneak Glove, Cat's Bell, X-Potion, Turbo Ether, Elixir, Megalixir, Dream Powder, Mute Mask, War Gong, Lovo Weed, Fire Fang, Antarctic Wind, Ice Crystal, Bold Plume, Swift bolt, Earth Drum, Earth Mallet, Deadly Waste, M-Tentacles, Stardust, Holy Touch, Ink, Vampire Fang, Ghost Hand, Dragon Scales, Impaler, Shrivel, Molotov, there's more, but I can't think of them right now.