Fuel cell powered electric motors are fast becoming a very plausible alternative to the more popular combustion engine. Fuel cells are electrochemical cells, a hydrogen fuel cell uses hydrogen as the fuel and oxygen as the oxidant, other forms of fuels cells also exist but obviously the preferable one would be the hydrogen fuel cell whose only by-product is water :). Fuel cells may seem to some as some 21st century miracle of modern technology but in reality fuel cells were first discovered by German scientist Christian Friedrich Schönbein in 1838!! Makes you kinda wonder why the technology has taken so long to reach the public arena (I smell a conspiracy :) ).
The Honda FC Sport - This car as well as the others below are all powered by hydrogen fuel cell stacks.