codes ported from Mame and CWcheat DB by lee4
9 type (m) codes provided and credits to: bfoos

Metal Slug 6

(M) CB6+/GS3+/XP4+
902E3344 0C0BF04D 

Alt. (M) CB6+/GS3+/XP4+
903099D8 0C0C261E 

(M) CB/GS/XP
F01173D4 002E3347

(M) good for ARmax
F02E3344 002E3347

(M) AR2v2/Gs2v2 
0E3C7DF2 1456E7A5
F01173D4 002E3347

Joker
P1
D0531642 0000????
P2
D0531A42 0000????

Language Mod
20117CD8 240200??
00=Japanese
01=English

P1 - Infinite Lives
012FB4FF 00000064

P1 - Infinite Arms
112DA5C8 0000FFFF

P1 - Infinite Bombs
012DA5C5 00000063

P1 - Invincibility
012DA588 00000069

P2 - Infinite Lives
012DADB7 00000064

P2 - Infinite Arms
112FB1D0 0000FFFF

P2 - Infinite Bombs
012FB1CD 00000063

P2 - Invincibility
012FB190 00000069

P1 - Weapon Modifier (block#1)
012DA5D0 000000??
012DA5D4 00000014

P1 - Weapon Modifier (block#2)
012DA5D1 000000??
012DA5D6 00000014

P2 - Weapon Modifier (block#1)
012FB1D8 000000??
012FB1DC 00000014

P2 - Weapon Modifier (block#2)
012FB1D9 000000??
012FB1DE 00000014

Weapon Modifier Digits
00 = Normal Gun
02 = Shotgun
03 = Rocket Launcher
04 = Flame Shot
05 = Heavy Machine Gun
06 = Laser Gun
07 = Big Shotgun
08 = Big Rocket Launcher
09 = Big Flame Shot
0A = Big Heavy Machine Gun
0B = Big Laser Gun
0C = Enemy Chaser
0D = Iron Lizard
0E = Drop Shot
0F = Super Grenade 
12 = Two Machine Gun
13 = Z Sword