Check out the 64 Boy. Someone spent around 80 hours hacking apart an N64, Gamecube controller and various other gadgets to build a portable N64.
The 64 Boy has a number of features that includes an output port for extra controllers to be used as well as sending the signal out to a TV.
It appears that it plays all games and is completely unique. If you are interested in buying it, check out the Youtube video details where information is provided. At the time of writing this, it is still available to buy.
Via: CrunchGear
I want it