Donkey Kong 64 for the Nintendo 64. I have never played a game that has come close to the entertainment value, nor as long of gameplay.
This year I had some extra $$$ from my birthday so I purchased an old DK64 limited edition N64. The bundle came with the game and a few other extras. Really brought back some of my childhood.
THERE'S ALWAYS MONEY IN THE BANANA STAND #TEAMCONNOR