Famicon - Microphone in the controller. The eject button (The button was there for no other reason than to make cartridges pop up for fun. It's literally unnecessary otherwise).
NES - R.O.B, NES Zapper, a bunch of other peripherals. This thing was entirely designed as a gimmicky toy.
N64 - The slot on the controller for the rumble pack (now a standard feature), the analog stick (now a standard feature), c-buttons (aka: Camera-buttons, now a standard feature in the form of a second analog stick). All things that people labeled as silly gimmicks that wouldn't catch on, especially since marketing was mostly "look at our weird controller!"
Gamecube - Designed with the intent on being the first portable home console to be used with the Gamecube TV screen and Gamecube portable battery pack. Ever wondered why it's so small, light and has a carry handle built in? That's mostly why.
It was also originally supposed to have motion controllers (see 'Wii') and had a few games in development for them, though they were obviously scrapped.
They also intended the GBA to connect to the Gamecube for 'reasons' (see 'Wii U') as a launch feature. I think it was delayed as games that used this feature were still in development on release, though console/handheld connectivity was planned during the console development.
Wii - Self explanatory.
Wii U - Self explanatory.
The only home console that really didn't really have any gimmicks was the SNES (do correct me if I'm wrong), though it did have the totally useless eject button like the Famicon. The handhelds were less gimmicky (up until the DS obviously) but still, they had their moments.