Green Lantern

Test pilot Hal Jordan is given a power ring by a dying alien and finds himself enlisted in the Green Lantern Corps, an interstellar police force with thousands of members, answering to a race of small blue immortals. The ring can make anything its wearer imagines, except, for reasons of plot, anything involving the colour yellow.

The Silver Age made superheroes into space opera, and Green Lantern is where that shows most clearly. The idea of a galactic police corps has since given the franchise decades of cosmic war stories.