Recent all-sky surveys have discovered a number of transients showing
unprecedented observed properties. A few of them are underluminous
(-10>M>-15) and cover the luminosity gap for transient events that
separates classical novae from traditional supernovae. Others are
among the brightest stellar explosions ever observed. In this talk
spectroscopic and photometric data of some of the most astonishing
unusual transients are presented, along with what we currently know on
the nature of their progenitor stars.