One of the coolest possibilities of using hydrogen fuel cells in cars, other than the fact that they don't need gasoline, is that the entire engine can be made into a flat rectangle, eliminating the bulky engine block that sits under the hoods of current gasoline-powered cars. This leaves room to design whatever type of space you want for the vehicle, as seen here in this fuel-cell concept car from GM. With no engine up front, the space is wide open, with a huge windshield and even a window where the front grille would be. Also, fuel cells have no emissions other than nice, environmentally friendly H20, so if you drive one you'll have a clear conscience about your driving — assuming you don't run down any hobos. Of course, fuel cells are still too expensive to mass produce, and this thing goes from 0 to 62 mph in about 16 seconds, so don't expect to be hitting the road or any people in one anytime soon.
Working Prototype: GM Hy-Wire Concept, via Gizmodo