  What makes a supernova truly `peculiar?' In this chapter we attempt to
address this question by tracing the history of the use of `peculiar' as a
descriptor of non-standard supernovae back to the original binary spectroscopic
classification of Type I vs. Type II proposed by Minkowski (1941). A handful of
noteworthy examples (including SN 2012au, SN 2014C, iPTF14hls, and iPTF15eqv)
are highlighted to illustrate a general theme: classes of supernovae that were
once thought to be peculiar are later seen as logical branches of standard
events. This is not always the case, however, and we discuss ASASSN-15lh as an
example of a transient with an origin that remains contentious. We remark on
how late-time observations at all wavelengths (radio-through-X-ray) that probe
1) the kinematic and chemical properties of the supernova ejecta and 2) the
progenitor star system's mass loss in the terminal phases preceding the
explosion, have often been critical in understanding the nature of seemingly
unusual events.
