For me, it's the Wii U controller.
I love the Wiimote/nunchuk combo. All it needed were some more buttons and continued improvement on the Motion + tech. And if you really wanted to appease the doubters, throw an analog stick on the Wiimote, so that you can even have dual analog.
But no, the obstinate hardcore whiners won out over a superior control method simply because it was *gasp* new, despite being capable of offering the exact same physical experience as a standard pad. Yes, the Wii U supports Wiimotes, but they are clearly not the emphasis on the new console.
Nintendo, without the courage of their convictions, reverted to an ugly dual analog pad, but simultaneously tried to "innovate" by aping the iPad with the near-useless gimmick of watching your Nintendo games (finally in HD) on a 5 1/2" screen. And with absolutely zero compelling software to justify the WiiPad (probably because anything that could be done with it also could've been done on DS), the response was tepid as expected.
Yeah, Skyrim and Dragon age were bad for fans, but those are just a couple of games. PSN is unfortunate, but you can't stop hackers if they want your shit. But the Wii U controller? I've gotta deal with this shit for the next 5 years.