Here is a lot of cool codes.
Refill Health in Giant Bowser Battles (Select)
Credits to pudquick of Gbatemp
and me for making it work (Button Activator) :P
94000130 fffb0000
1210e12e 0000012c
d2000000 00000000
L+R to clear Cholestroad River
94000130 fcff0000
02056020 00ffff00
d2000000 00000000
Gauntlet Minigame's Bosses HP 0 (Select)
94000130 fffb0000
12128226 00000000
1212834a 00000000
1212846e 00000000
12128592 00000000
121286b6 00000000
121287da 00000000
d2000000 00000000
Infinite HP Flower Minigame
9233a2d8 000003ff
2233a2dc 00000002
d2000000 00000000
Most credits to gbatemp.net members.