  Supernovae arise from progenitor stars occupying the upper end of the initial
mass function. Their extreme brightness allows individual massive stars to be
detected at cosmic distances, lending supernovae great potential as tracers of
the upper end of the IMF and its evolution. Exploiting this potential requires
progress in many areas of supernova science. These include understanding the
progenitor masses that produce various types of supernovae and accurately
characterizing the supernova outburst and the environment in which it was
produced. I present some preliminary work identifying the environmental
conditions that produce the most luminous supernovae, believed to arise from
stars with masses greater than 100 M_sun. I illustrate that the presence of
these extreme supernovae in small star-forming dwarfs can be used to test our
understanding of the upper end of the IMF.
