There's a lot to choose from, I know, but this - called simply "The Video Game Song" - is probably my all-time favourite... video game song.
I actually picked up the album this is from, Sole's Learning to Walk, in a second-hand store around 6-7 years ago. First time I listened to it, I blew straight past it, not paying any attention to the lyrics.
Second time though, oh boy. I don't like it for its sparse production, or monotonous delivery (aided by Sole's former Anticon labelmate Alias), but I'll be damned if that's not the most constructive use of a lifetime's worth of video gaming I've heard in a rap song. It's exhaustive.