Kingdom Hearts II: Final Mix +

Go to you tube and look up the channel "Antiwepon" he has awesome codes and videos

I have a Japanese Pro Action Replay 2, which I believe is the same as the Gameshark 2 v2. I found these codes at this awesome Japanese site: mutuki1406.hp.infoseek.co.jp/code/kh2_fm.html
Everything is in Japanese, but here are a few codes I have used myself:

Master Code:
EC878540 142F1110

Have 999 of all materials during synthesis: (You will not really have the items, but you can synth as much as you want!)
1C9AF3F4 3852E404
1C9AF3F8 15F6E79D
1C9AF3FC B092E7A5
0D652956 14566359
1D652958 105393D5

Receive 32 times the experience than normal:
1C9AF334 0C5893D1
1C9AF338 145A0665
1C8EC5C8 105393A8
1C8CD350 0C5393A8

HP does not go down: (This code allows you to never lose life as long as no hit hurts for more than your Max HP)
1C9AF328 90D4E7A1
1C9AF32C 0C585EAB
1C9AF330 B0D4E7A5
1C81EF00 105393A5

Enjoy!