superrare
rare as a four-leaf clover
rarer than hens' teeth
rare as rocking horse shit
ultrararefied
one in a million
ultrarare
rare
rare as hen's teeth
rocking horse shit
semirare
rareish
historically
uncommon
geason
unique
attenuate
remarkable
few and far between
sporadic
rarity
unusual
rarefiable
once in a purple moon
antrin
freak accident
rarefactional
once-in-a-lifetime
uncommonly
nonrare
rarely
outré
in a pig's eye
sporadicalness
unwontedly
supersubtle
seldomness
rara avis
unicorn
scarce
black swan
dead donkey
isanomal
exceptional
unobtainium
once in a blue moon
atypical
uncommonness
feat
rarefication
different
rarissima
superabnormal
rareness
extraordinary
seldomly
freakish
no great shakes
hellacious
anomalism
phenomenon
offbeat
rare bird
unchancy
out of the common
out of the way
minimum
minimal
inimicable
impossible
miscegenative
long shot
miscegenic
miscegenistic
sporadical
one-shot
fremd
commonplace
inconceivability
not grow on trees
seld
man bites dog
unusualness
last
extraneity
seldom or ever
thin on the ground
see the dark side of the moon
big if
recherche
suckfest
quaint
shitfest
mystery
crackpot
something else