A group of engineering students at the Delft University of Technology, Netherlands, have built that worlds largest NES controller as part of a promotion for the 2012 Guiness World Records Gamer's Edition. The control is fully functional, and is built to a 30:1 scale. The students have said that it cost them around £4,000 to build.
I personally would love to use it, but i bet it makes the games a LOT harder to play, and you will need a friend to play as well. Who needs party games when you can play NES at 30:1 scale?