Sora's Ultima Weapon
Sora's Ultima Weapon is obtained through item synthesis. Once you have obtained seven Orichalcum + s and the other ingredients, you will be able to synthesize it if you have an Energy Crystal. Note: You must be at least a level 2 Moogle to use energy items (for example, shards, stones, gems, and crystals). The items required are as follows:
Go to the mansion in Twilight Town. This is towards the end of the game when you go with Sora. Once the machine is up and running to go to Roxas's Twilight Town, do not enter it. Instead, go through the other room where you went to fight Axel with Roxas at the start of the game. Then, go into the next room with the hallway with the pods where Goofy and Donald were found. There are a few chests in there; the Ultimate Recipe is the in the chest next to Donald and Goofy's pod.
Seven Orichalcum +
1. Clear Atlantica.
2. Clear 100 Acre Wood.
3. Find the chest in the World That Never Was at the Brink Of Despair just before you go into the castle. There will be a big chest next to the save point. This is not the Orichalcum +. Turn around at this location and follow the short path across from the save point with the Orichalcum + chest.
4. Clear Goddess Of Fate Cup in the Underworld Coliseum.
5. Chest in Twilight Town, in Sunset Terrace where you went earlier in the game for the Seven Wonders. Jump on top of the train and you will see a chest on the roof of the big building (the one closest to to the sunset station).
6. Chest in Space Paranoids during the second visit there, just before you fight Commander Sark and the MCP.
7. Collect all Material in the game and give it to the Synthesis Moogle. He will give you an Orichalcum +. You need every single Material (shards, stones, gems, and crystals, including a regular Orichalcum).
Energy Crystal: Required to halve the amount of Orichalcum + s you need. Dropped by Bookmasters in Radiant Gardens (Hollow Bastion) near Merlin's house. These are the characters that float with green hats and books.
Twilight and Dense Crystals: Nobodies on Naught's Skyway. Go to naught's skyway just after the Hall Of Empty Melodies. Fight the Nobodies there and they will drop Twilight and Dense items.
Serenity Crystals: You can get these from the Moogles for giving them complete sets of Materials.
Mythril Crystals: Found in random item chests.
Gummi Ship bonuses
Berserk mode: Reach Metal Level 30.
Gummi Ship Level 2: Successfully complete Level 1 with "S", "A", or "B" ranks.
Gummi Ship Level 3: Successfully complete Level 1 and 2 with "S", "A", or "B" ranks.
Special Models: Get an "S" rank in the Gummi Ship missions.
Synthesis Moogle bonus items
Give the following items to the Synthesis Moogle to get the corresponding bonus item:
AP Boost: Give all Mythril Materials
AP Boost: Five 25 types of Material
Defense Boost: Give all Bright Materials
Elixer: Five one type of Material
Free Development: Give 5 types of Material
Free Development 2: Give 20 types of Material
High Drive Recovery: Give 10 types of Material
Megalizer: Give 15 types of Material
Serenity Shard: Give a total amount of 50 or more Materials
Serenity Shard 2: Give a total amount of 100 or more Materials
Donald's enemy items
Nobody Lance: Kill the flying Nobodies that carry spears until you get the Nobody Lance. This is best done in the Beast's Castle.
Shaman's Relic: Go to the Pride Lands, then go to Wildebeest Valley. Equip Lucky Lucky to all your party members, then kill the Shamans until you get the Shaman's Relic.
Goofy's enemy items
Akashic Record: Kill the book-wielding Heartless in Radiant Garden (Hollow Bastion) until you get the Akashic Record.
Heartless Shield: Go to Port Royal and kill all the enemies until you get the Heartless Shield.
Nobody Guard: Find and kill the Gambling Nobodies until you get the Nobody Guard. Note: This may take some time.