For centuries, we have known that our dynamic universe is adorned by cosmic fireworks: energetic and ephemeral beacons of light from a single star that are a million (nova) to a billion (supernova) times brighter than our sun. However, it had been an age-old conundrum that the brightest nova is approximately 1000 times fainter than the faintest supernova; why should nature leave such a wide "gap"? In search of an answer, I undertook three systematic surveys for my thesis. Since I was looking for transients fainter, faster and rarer than supernovae, I focused my search on galaxies in the local universe. We now have convincing evidence of multiple, distinct populations of rare transients bridging this "gap". Perhaps, we are witnessing new stellar physics- shell detonations in ultra-compact white dwarf binaries, electron-capture supernovae, white dwarfs collapsing into neutron stars and birth of black-holes. A small number of intensively followed-up discoveries of elusive transients...