Your Favourite Video Game Chiptunes

What's your favourite or most memorable video game chiptune? I don't mean just any video game music, I mean older stuff.

For me it's the battle theme from Pokémon Gold and Silver. I played Red and Blue, but I wasn't completely obsessed until G/S. I put hundreds of hours into my copy of Gold, and when my brother got tired of his copy of Silver, I started a new game and traded with myself to complete my Pokédex. So, needless to say, I heard this track a lot.