Before the Nintendo GameCube was released, I received this promotional preview minidisc from somewhere... I don't even remember where, but it looks like it might've come in the mail.
Even though it looks like a GameCube game, it's only playable on a computer and it has a Flash menu from which you can see information on the console, screenshots and trailers for upcoming games, and get wallpapers for your computer. There are also some outdated links to Nintendo websites like Nintendo Power and Nintendo Cube Club.
Check out the video tour I recorded of the interface and information inside. Interestingly, it advertised an SD-Memory Card Adapter, which I don't remember ever being officially released.
The disc contains previews for a bunch of early Gamecube games: Star Wars Rogue Squadron: Rogue Leader, Wave Race: Blue Storm, Tony Hawk's Pro Skater 3, Star Fox Adventures: Dinosaur Planet, SSX Tricky, Super Smash Bros. Melee, Pikmin, NBA Courtside 2002, Madden 2002, Luigi's Mansion, and Extreme-G 3. If you want, you can watch all of the trailers as they are on the disc here: