The following are known Gecko Codes for Grand Slam Tennis on Nintendo Wii (Wii).

Any profile all stars, abilities, clothing and gear [joecamel]
42000000 92000000
00A5A017 0000000A
08A5A18C FFFFFFFF
200D0004 00000000
E0000000 80008000
After loading profile, go back to main menu and reload profile.

Reset cpu score to zero - press 1 [joecamel]
28279DC0 FDFF0200
48000000 8028D1F8
DE000000 90009340
14000094 00000000
E0000000 80008000

Give player match point - press 2 [joecamel]
28279DC0 FEFF0100
48000000 8028D1F8
DE000000 90009340
14000090 00000003
140000A0 00000005
E0000000 80008000
This is for one set per match, if you want more sets use custom code below

Custom give player match point - press 2 [joecamel]
28279DC0 FEFF0100
48000000 8028D1F8
DE000000 90009340
14000090 00000003
140000A0 00000005
140000F0 0000000X
E0000000 80008000
If sets per match = 1, X should = 0
If sets per match = 3, X should = 1
If sets per match = 5, X should = 2