The Nintendo DS
Back in 2004, it was supposed to be a new start for Nintendo. As the late Hiroshi Yamauchi put it, if it were to succeed, Nintendo would rise to heaven. If not, it would sink to hell. And at first glance, the DS looked doomed to fail. Stacked next to Sony's elegant and powerful PlayStation Portable (which boasted PS2 quality in your pocket), the DS stood out with it's weird dual screen setup, touch screen, microphone,and comparatively weaker specs.
It didn't even have a strong launch lineup, with the only must-have title at launch being an enhanced N64 port with somewhat gimped controls. Yet against all odds, Nintendo was able to prove the DS' worth thanks to unique titles like Nintendogs and Brain Age, and the eventual DS lite upgrade, which took the relatively ugly and fat design of the OG model, and made it a much sleeker, cooler gadget for the mainstream. Eventually, the DS racked up an impressive amount of third party support both east and west, with every major publisher seemingly announcing at least something for it each year.
Perhaps what I find most interesting about the DS was Nintendo's own output. In an odd twist of fate, Nintendo's output was generally considered sub-par among fans, at least in regards to Nintendo staples like Zelda, Mario, and Metroid. The DS had strong third party support, but it was very rare for a Nintendo console to be considered to have worse first party support than third party. Yet, despite that, I consider the DS to host Nintendo's most unique and intruiging new IP output of any of their consoles. Obviously you had the aforementioned Touch Generations stuff like Brain Age and Nintendogs, but you also had weirder stuff like Rhythm Heaven, Hotel Dusk, Elite Beat Agents, Electroplankton, etc. That's not even getting into their Japan only games like Daigasso! Band Brothers, the Tingle games, Chōsōjū Mecha MG, Jet Impulse, etc. They co-produced two Shonen Jump fighting games. Even some of the established franchises were taken in weird directions. Kirby Canvas Curse was one of the earliest showcases of the DS' touch screen, Wario Ware D.I.Y. put the Microgame creation into the player's hands. Mario Kart DS marked Nintendo's very first foray into the brave new world of online multiplayer, Advance Wars took a darker turn with Days of Ruin, and the aforementioned Metroid Prime Hunters turned Metroid into a DS equivalent of a portable Quake III.