The following are known CWCheat Codes for Metal Slug XX on Sony Playstation Portable (PSP).

_S ULUS-10495
_G Metal Slug XX [US]
_C0 1P Activate Gun SLOTS
_L 0x005001CE 0x000000FF
_L 0x105001DE 0x0000FFFF
_L 0x105001E0 0x0000FFFF
_L 0x105001E2 0x0000FFFF
_C0 1P Add Saved POW
_L 0xD0000000 0x10002008
_L 0x30100001 0x00552E28
_C0 1P Bomb Select
_L 0xD0000000 0x10000111
_L 0x005001D0 0x00000001
_L 0xD0000000 0x10000141
_L 0x005001D0 0x00000002
_C0 1P Custom Gun SLOT1
_L 0x005001DB 0x00000013
_C0 1P Custom Gun SLOT2
_L 0x005001DC 0x00000007
_C0 1P Custom Gun SLOT3
_L 0x005001DD 0x00000014
_C0 1P Disable Coins/Combo system
_L 0x105001E8 0x000000FF
_L 0x005001EA 0x00000000
_C0 1P Enable Leona Heidern
_L 0x00141F54 0x00000001
_C0 1P Harakiri
_L 0xD0000000 0x10000301
_L 0x005001BB 0x00000002
_C0 1P INF Bombs for Metal Slugs
_L 0x105530E6 0x0000FFFF
_C0 1P INF Time
_L 0x10589D88 0x0000FFFF
_C0 1P Invincible
_L 0x00500198 0x00000001
_C0 1P Max Ammos & Bombs
_L 0x105001D4 0x0000FFFF
_L 0x005001D1 0x00000063
_C0 1P Max Lives
_L 0x00500457 0x00000009
_C0 1P Mod Gun NOW!!
_L 0xD0000000 0x10004110
_L 0x005001CF 0x00000007
_L 0xD0000000 0x10004110
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10004120
_L 0x005001CF 0x00000008
_L 0xD0000000 0x10004120
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10004140
_L 0x005001CF 0x00000009
_L 0xD0000000 0x10004140
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10004180
_L 0x005001CF 0x0000000A
_L 0xD0000000 0x10004180
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10002110
_L 0x005001CF 0x00000013
_L 0xD0000000 0x10002110
_L 0x005001B5 0x00000000
_L 0xD0000000 0x10002120
_L 0x005001CF 0x00000014
_L 0xD0000000 0x10002120
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10002140
_L 0x005001CF 0x0000000D
_L 0xD0000000 0x10002140
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10002180
_L 0x005001CF 0x0000000E
_L 0xD0000000 0x10002180
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10008110
_L 0x005001CF 0x0000000F
_L 0xD0000000 0x10008110
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10008120
_L 0x005001CF 0x00000012
_L 0xD0000000 0x10008120
_L 0x005001B5 0x00000002
_L 0xD0000000 0x10008140
_L 0x005001CF 0x0000000B
_L 0xD0000000 0x10008140
_L 0x005001B5 0x00000001
_L 0xD0000000 0x10008180
_L 0x005001CF 0x0000000C
_L 0xD0000000 0x10008180
_L 0x005001B5 0x00000001
_C0 1P Play as Leona Heidern
_L 0x00500180 0x00000006
_L 0x00500456 0x00000006
_C1 1P Play as Leona Heidern
_L 0x00500180 0x00000006
_L 0x00500456 0x00000006
_C0 1P Rapid Attack
_L 0x005001CC 0x00000001
_L 0x005001CD 0x00000001
_C0 1P Skill Eri's Bomb
_L 0xD0000000 0x10008000
_L 0x00500180 0x00000002
_C0 1P Skill Ralf's Armor
_L 0x004CA405 0x00000027
_C0 1P Skill Tarma's Vulcan Fix
_L 0xD0000000 0x10004100
_L 0x00500180 0x00000001
_C0 99 Prisoners
_L 0x00552E28 0x00000063
_C0 Infinite 
_L 0x005001D1 0x000000FF
_C0 Infinite Ammo
_L 0x005001D1 0x0000FFFF
_L 0x0050045F 0x0000FFFF
_L 0x105001D4 0x0000FFFF
_L 0x1050044E 0x0000FFFF
_C0 Infinite ammunitions
_L 0x005001D4 0x000000FF
_L 0x0050044E 0x000000FF
_C0 Infinite bomb machine 
_L 0x105530E6 0x0000FFFF
_C0 Infinite bombs
_L 0x005001D1 0x000000FF
_L 0x0050045F 0x000000FF
_L 0x005530E6 0x000000FF
_C0 Infinite bombs 
_L 0x105001D4 0x0000FFFF
_C0 Infinite Life 
_L 0x00500457 0x000000FF
_C0 Infinite Lives
_L 0x00141154 0x0000FFFF
_L 0x00500457 0x0000FFFF
_C0 Invincible 
_L 0x00500198 0x00000001
_C0 machine energy diminished 
_L 0x205102FC 0x00000030
_C0 x99 1UP
_L 0x00500457 0x00000063
_C0 x99 Bombs
_L 0x005001D1 0x00000063