Final Fantasy XIII upgrades

Most weapons and accessories in Final Fantasy XIII are capable of having their levels increased with components. Once the maximum level (indicated with a star as opposed to the item level appearing in the menu next to the item) has been reached many are upgradable to another weapon or accessory altogether with catylist minerals. The ability to upgrade is given early in the game and accomplished at save points.

Accessory Upgrades

 * Diamond Bangle → Adaman Bangle
 * General's Belt → Champion's Belt
 * Witch's Bracelet → Magus's Bracelet

Weapon Upgrades

 * Axis Blade → Enkindler
 * Umbra → Solaris
 * Healer's Staff → Physician's Staff

Accessory Upgrades

 * Tungsten Bangle → Titanium Bangle
 * Power Wristband → Brawler's Wristband
 * Magician's Mark → Shaman's Mark
 * Ember Ring → Blaze Ring
 * Frost Ring → Icicle Ring
 * Spark Ring → Fulmen Ring
 * Frost Ring → Icicle Ring
 * Aqua Ring → Riptide Ring
 * Zephyr Ring → Gale Ring
 * Clay Ring → Siltstone Ring
 * Aurora Scarf → Nimbletoe Boots
 * Gold Watch → Champion's Badge

Weapon Upgrades

 * Organyx → Apocalypse
 * Aldebarans → Sadalmeliks
 * Tigerclaw → Wyrmfang

Accessory Upgrades

 * Adaman Bangle → Wurtzite Bangle
 * Power Glove → Kaiser Knuckles
 * Weirding Glyph → Magical Crest
 * Royal Armlet → Imperial Armlet
 * Ribbon → Super Ribbon

Weapon Upgrades

 * Procyons → Betelgeuse Customs

Accessory Upgrades

 * Iron Bangle → Silver Bangle

Weapon Upgrades

 * Millerite doesn't upgrade weapons.

Accessory Upgrades

 * Mithril Bangle → Platinum Bangle
 * Collector's Catalog → Connoisseur's Catalog
 * Speed Sash → Energy Sash
 * Fire Charm → Twenty-sided Die
 * Ice Charm → Twenty-sided Die
 * Lightning Charm → Twenty-sided Die
 * Water Charm → Twenty-sided Die
 * Wind Charm → Twenty-sided Die
 * Earth Charm → Twenty-sided Die

Weapon Upgrades

 * Mnar Stone doesn't upgrade weapons.

Accessory Upgrades

 * Titanium Bangle → Gold Bangle
 * Metal Armband → Ceramic Armband
 * Serenity Sachet → Safeguard Sachet
 * Giant's Glove → Warlord's Glove
 * Glass Buckle → Tektite Buckle
 * Glass Orb → Dragonfly Orb
 * Star Pendant → Starfall Pendant
 * Pearl Necklace → Gemstone Necklace
 * Warding Talisman → Hexbane Talisman
 * Pain Dampener → Pain Deflector
 * White Cape → Effulgent Cape
 * Rainbow Anklet → Moonbow Anklet
 * Cherub's Crown → Seraph's Crown
 * Guardian Amulet → Shield Talisman
 * Auric Amulet → Soulfront Talisman
 * Watchman's Amulet → Shrouding Talisman
 * Hero's Amulet → Morale Talisman
 * Saint's Amulet → Blessed Talisman
 * Zealot's Amulet → Battle Talisman
 * Flamebane Brooch → Flameshield Earring
 * Frostbane Brooch → Frostshield Earring
 * Sparkbane Brooch → Sparkshield Earring
 * Aquabane Brooch → Aquashield Earring
 * Hermes Sandals → Sprint Shoes
 * Champion's Badge → Survivalist Catalog

Weapon Upgrades

 * Blazefire Saber → Flameberge
 * Edged Carbine → Rainbow Wing
 * Wild Bear → Feral Pride
 * Unsetting Sun → Midnight Sun
 * Binding Rod → Hunter's Rod
 * Pearlwing Staff → Brightwing Staff
 * Rod of Thorns → Orochi Rod
 * Vega 42s → Altairs
 * Deneb Duellers → Canopus Amps
 * Pleiades Hi-Powers → Hyades Magnums
 * Bladed Lance → Grave Lance
 * Partisan → Rhomphair

Rhodochrosite
Accessory Upgrades

Silver Bangle → Tungsten Bangle

Whistlewind Scarf → Aurora Scarf

Scarletite
Accessory Upgrades

Warrior's Wristband → Power Glove

Sorcerer's Mark → Weirding Glyph

Tetratic Crown → Tetratic Tiara

Weapon Upgrades

Lifesaber → Peace Maker

Lionheart → Ultima Weapon

Paladin → Winged Saint

Power Circle → Battle Standard

Sacrificial Circle → Indomitus

Mistilteinn → Erinye's Cane

Spica Defenders → Sirius Sidearms

Trapezohedron
Upgrades all Tier 2 weapons to Tier 3 weapons. The names of Tier 3 weapons are the same no matter what was upgraded, depending on character:

Lightning - Omega Weapon

Snow - Save the Queen

Vanille - Nirvana

Sazh - Total Eclipses

Fang - Lance of Kain

Hope - Nue

Uranintite
Accessory Upgrades

Gold Bangle → Mithril Bangle

Brawler's Wristband → Warrior's Wristband

Shaman's Mark → Sorcerer's Mark

Blaze Fire Ring → Salamandrine Flame Ring

Fulmen Ring → Raijin Ring

Icicle Ring → Boreal Ring

Riptide Ring → Nereid Steam Ring

Siltstone Ring → Galan Ring

Gale Ring → Sylphid Ring

Black Belt → General's Belt

Rune Bracelet → Witch's Bracelet

Survivalist Catalog → Collector Catalog

Hunter's Friend → Speed Sash

Entite Ring → Goddess's Favor

Weapon Upgrades

Gladius → Helter Skelter

Hauteclaire → Durandal

Rebel Heart → Warrior's Emblem

Feymark → Soul Blazer

Belladonna Wand → Marlboro Wand

Heavenly Axis → Abraxas

Rigels → Polaris Specials

Antares Deluxes → Fomalhaut Elites