Nintendo has a knack for cranking out interesting, bizarre, and pointless peripherals for its game systems. Some add-ons are better than others (and there's an episode of the Power Button podcast that focuses on this topic), what what's really strange about Nintendo's track record for accessories is that they don't necessarily support them for very long. You have to admire that strange mixture of optimism and abandonment. Jeremy Parish at USgamer has taken a look at what he calls "Mario's Orphans": Nintendo peripherals sent to die such as the four-player adapter for the Game Boy, the Wii Speak microphone (which truly is stone dead now that the service driving it has ceased to be, and I'd just like to brag that I predicted that back in 2008), the Super NES mouse, and the GameCube broadband adapter.
While Microsoft was making a splash with Xbox Live, and Sony was exploring online through games like SOCOM and Monster Hunter, Nintendo made its own inroads onto the Internet with GameCube. No, just kidding. They released a peripheral that basically just supported Phantasy Star Online.
Well, technically, the Broadband Adapter also supported a trio of Nintendo racing games, but strictly for local play on a closed network. Only Sega (and Chunsoft with a single Japan-only release called Homeland) managed to get GameCube online in a compelling way, and even then that was just to give a little extra life to a Dreamcast RPG. If that system hadn't gone the way of the dodo, the Broadband Adapter would have been completely pointless. In this case, Sega literally did what Nintendon't.
There's no mention of the DK bongo drums which worked with the Donkey Konga series and Donkey Kong Jungle Beat, but of all the limited support accessories in my collection, the drums are definitely the largest. Then there's the Action Pad dance mat for Dance Dance Revolution: Mario Mix, the GameCube's microphone that plugged in through the console's memory card slots, and the Rumble Pak for the Nintendo DS which was rendered pointless once the DS series was redesigned to remove the secondary data slot. Nintendo even went the extra mile to remove Rumble Pak support from some DS games that worked with the accessory in other territories once the DSi branch became the defacto available DS. That's just adding insult to injury.