Disco Ball
Though the concept predates it, Louis B. Woeste created the Myriad Reflector which we accept as the modern starting point of what we think of as the disco ball.
We all think disco on sighting this spinning, reflective relic of the seventies, but the disco ball's origin predates light up dancefloors, bouffants, and tight-crotched flares by some 75 years. Though unpatented or mass produced, it's reported a group of electricians in Charlestown, Massachusetts lit up their 1897 annual union party, bouncing an arc light off a cluster of small mirrors on a sphere.
It would be another twenty years before Louis Bernard Woeste, working out of Newport, Kentucky, filed the first real patent in 1917 for what he formally named the 'Myriad Reflector' -- a "polyhedron of numerous faces" designed to scatter moving, varied color spots across a room.
Disco itself wouldn't exist for another five decades. By the time the mirror ball became inseparable from the 1970s dance floor, Woeste's original name had vanished from the general lexicon, making way for the unimaginative term "mirror ball." The trail does follow him, however. A 1979 patent for a portable home "discotheque," complete with myriad reflector, cites Woeste's original design.
The disco ball as we know it today was not invented for disco -- existing at least five decades before the genre it's now synonymous with.