unrepeatable
million-dollar
uniquely
unambiguously
specific
one and only
out of the common
unaccustomed
rare bird
specialism
rara avis
one-off
antrin
peculiarsome
streak
unusuality
way-out
freakish
unusual
speshul
spesh
remarkable
one-of-a-kind
fremd
quaint
first-of-its-kind
queer as a clockwork orange
geason
mutant
distinctive feature
offbeat
peculiar
distinguishing characteristic
peculiarity
non-imitation
self
extraordinary
rarity
freaky
unorthodox
idiomorphous
one-shot
distinctify
far-out
unmistakable
anomaly
unusual person
sole
snowflake
uncharacteristic