The ARC reactor -- "affordable, robust, compact reactor" -- is a nuclear fusion reactor, still in concept stage, that could allow for smaller and cheaper reactors that would make fusion power practical within the next decade.
This reactor uses new commercially available superconductors that are capable of producing high-magnetic field coils. The resulting fields do a better job at confining superhot plasma, making the reactor smaller and cheaper.
The ARC reactor looks set to go a long way towards aiding in the development of a commercially viable fusion reactor -- something which would make all conventional electricity sources obsolete. If realized, these sorts of reactors would offer an unlimited source of power, improving every single aspect of human existence.