The following are known Action Replay Codes for Pokemon XD: Gale of Darkness on Nintendo GameCube (GCN).

Master Code – Must Be On
MBJX-CMVT-1XDM6
V9TR-XQZQ-6NX80
8JKU-WUUV-AM4VB
7J3T-X2RQ-DVYXJ
P669-Y9AW-ZU3J5
P7QD-ETW4-1E3T0
A9PZ-99MP-N69CC
3X1D-4E8Q-443MB
W3B4-7MEH-9ZJPZ
VBG7-4N52-TGAND

Infinite Money
C85J-749N-QBR04
7FGB-M8AT-T80HN
RR4W-BHZ7-VNMQQ

Infinite Poke Coupons
N8R6-T2W2-4573C
6M8U-9RWQ-569D5
HGVR-CDRA-NDMF6

Hold R While Gaining EXP For Super Level Up
B7JB-ETHQ-87ZHX
XZ0C-BGRD-N1EE5
W54Z-XZ2X-FNHKE