Almost by definition, concept gadgets are some of the coolest things going. They're fun to look at, and probably fun to play with, assuming you and they were ever in the same room. But that's the other thing about concept gadgets--they may never venture far beyond the lab or the press release. Consider for the moment the apple-shaped remote control from Sony, the Toast Messenger, and Rinspeed's Squba Diving Car.
They're all here--with lots more eye candy to boot--in Smashing Magazine: "Monday Inspiration: Innovative Designs and Devices"