The new Xbox One controller may not look too different from its predecessor, but Microsoft spent millions of dollars developing prototypes--some which were truly "out there." For example, one prototype actually emitted smells.
"We had a whole bunch of brainstorm sessions and built hundreds of models," Microsoft's Zulfi Alam said. "We looked at concepts like adding displays to the controller. We looked at concepts like adding smell."
"We built small slugs of different types of smells that could actually come out of a controller," Alam told VentureBeat. "Like, as you walked through a jungle, you'd smell the flora."
Other options considered by Microsoft are features found in their competitor's controllers, including a touchpad a la PS4 and camera a la Wii U. They even considered built-in speakers to the controller, much like DualShock 4 and GamePad, but decided that it wasn't better than what the TV could do. "You've got a great TV with a better speaker than we could ever put in this controller... We really want them to be immersed in the experience that's happening in front of them."
One of the coolest ideas explored by Microsoft would've emulated their impressive IllumiRoom idea. By throwing in a tiny projector in the front of the controller, it could beam out ambient visuals around the player. Unfortunately, it was a huge battery drain on the controller, which led it to the cutting room floor.