It's not recommended to cheat in this game. Most cheats cause you to end up freezing at Chapter 5, even if you turn them off. (They permanently damage your Save.)
Only a few codes are known to be working.
Code:
gametitle=Valkyrie Profile 2: Silmeria [SLUS 21452] (U) [CC96CE93]
comment=Patch by Ryudo
// ----------------------------------
// [ Misc Codes ] -------------------
// ----------------------------------
// Ignore GameGuard (prevents freezing)
patch=1,EE,FE129B51,extended,800813BF
patch=1,EE,000FFFFE,extended,0000022D
patch=1,EE,000FFFFF,extended,0000022D
patch=1,EE,9013A550,extended,0C04E8FC
patch=1,EE,E0033B40,extended,0035EC8C
patch=1,EE,104234AA,extended,00001000
patch=1,EE,10423662,extended,00001000
patch=1,EE,1042382A,extended,00001000
patch=1,EE,E0027EC0,extended,0049550C
patch=1,EE,2049BCB0,extended,03E00008
patch=1,EE,2049BCB4,extended,00000000
patch=1,EE,E007E140,extended,0036D90C
patch=1,EE,203683D4,extended,00000000
patch=1,EE,103AD16A,extended,00001000
patch=1,EE,103AD61E,extended,00001000
patch=1,EE,10430B76,extended,00001000
patch=1,EE,10430BE2,extended,00001000
patch=1,EE,10431A66,extended,00001000
patch=1,EE,10431C1E,extended,00001000
patch=1,EE,D0397CAC,extended,0000102A
patch=1,EE,20397CB0,extended,00000000
// All Items (Turn it off after you obtain the Items, save your game, load without this cheat enabled via Memory Card)
patch=1,EE,2030D1B8,extended,240F03E7
patch=1,EE,2030D1BC,extended,0080702D
patch=1,EE,2030D1C0,extended,240D0063
patch=1,EE,2030D1C4,extended,A1CD0002
patch=1,EE,2030D1C8,extended,25EFFFFF
patch=1,EE,2030D1CC,extended,15E0FFFD
patch=1,EE,2030D1D0,extended,25CE0004
// View Camp Menu for Max Oth (Money)
patch=1,EE,E0085821,extended,00460AB4
patch=1,EE,200C0240,extended,3C01323B
patch=1,EE,200C0244,extended,3421875C
patch=1,EE,200C0248,extended,AD01006C
patch=1,EE,200C024C,extended,03E00008
patch=1,EE,200C0250,extended,8D0B0004
patch=1,EE,20460968,extended,0C030090
patch=1,EE,10460AC6,extended,00001000
patch=1,EE,20460AC8,extended,AD0B0018
// View Camp Menu for Max Crystals
patch=1,EE,E0085821,extended,004608DC
patch=1,EE,200C0220,extended,3C017425
patch=1,EE,200C0224,extended,34218000
patch=1,EE,200C0228,extended,AD010078
patch=1,EE,200C022C,extended,03E00008
patch=1,EE,200C0230,extended,8D0B0004
patch=1,EE,20460790,extended,0C030088
patch=1,EE,104608EE,extended,00001000
patch=1,EE,204608F0,extended,AD0B0018
Those are all the codes you need. Don't mess with others.
Note: In order to trigger the 'All Items' code, you have to sell one item, or equip a weapon/armor on any character. Then you'll have a filled inventory after that.