Some are random and some are in treasure chests, things like lightning shards, twilight shards, dense shards and those kinds of things are found from heartlesses and nobodies. But things like Orichalcums you find from treasure chests, and some you can get from the heartless that looks like a candy machine
The heartless that you fight drop different types of items that you can use for item synthesis.
For info, check www.gamefaqs.com
You find all your answers for Kingdom Hearts on "wiki Kingdom Hearts"
If you mean the ultimate weapon, you get it by synthesizing specific items you get from noobodies, heartless and mushrooms throughout the game in both kingdom hearts 2 and kingdom hearts 1 (but not from noobodies because they don't exhist in that game). To find out what specific enemies you have to fight in order to get the ingrediants, go to ign.com and type in Kingdom hearts 1 or 2. Then look on the list of cheats for it.
Kingdom Hearts- Air Pirate, Battleship, Pirate Kingdom Hearts II- Aerial Knocker, Shaman.
There are no Gameshark codes for Kingdom Hearts 2.
Hot Topic, You can go on-line at hottopic.com and search kingdom hearts and there's a kingdom hearts necklaces and other things.
You have to earn them.
Items are found in chests, won as awards, dropped by enemies and can be bought in the Moogle Shop.
There is no possible way of finding Xemnas in kingdom hearts. You are only able of finding him in kingdom hearts 2, which he is the last boss in the game.
You can find Kingdom Hearts in: * Gamestop * Wal-Mart * Best Buy Hope this helps! =)
Kingdom Hearts backpacks, shirts, and other accessories are available at Hot Topic.