What cheat codes have remained in your memory to this day?

[Alex_The_Hedgehog]

Donkey Kong Country 3: L-R-R-L-R-R-L-R-L-R

MERRY - Christmas-themed bonus
WATER - Secret waterfall cave, all bonus coins
COLOR - Change characters colors
MUSIC - Sound test


Yoshi's Island:

Hold select and press X-X-Y-B-A to play minigames.