Donkey Kong Country 

Highlight "Erase Game" and enter the following: 
B, A, R, R, A, L:(BARRAL) 50 lives 
DOWN, A, R, B, Y, DOWN, A, Y:(DARBYDAY) Music test [press SELECT to go through 
the sounds] 
B, A, DOWN, B, UP, DOWN, DOWN, Y:(BADBUDDY) Two Player Competition Mode