The paper announcing the first laser was rejected — before Nature published it

In May 1960, Theodore Maiman built the first working laser — a ruby crystal pulsed with flashlamp light — at Hughes Research Laboratories, beating better-funded teams at Bell Labs and Columbia. Physical Review Letters rejected his short paper as unremarkable, so he published in Nature instead. Lasers now run eye surgery, barcode scanners, and the fiber-optic internet.

— Theodore H. Maiman, Stimulated Optical Radiation in Ruby — Nature, 1960