Answer: rarest

AnswerCrossword Clue
RARESTLike AB negative among blood types
RAREST"That ... gift . . . common sense": Meredith
RARESTMost attenuated
RARESTLeast occurrent
RARESTLeast done
RARESTLike a numismatist's greatest treasure
rarest(of an event, situation, or condition) Not occurring very often
rarestRARE, uncommon (fairly rare)
rarestUnusually good or remarkable
rarest(of a thing) Not found in large numbers and consequently of interest or value
RARESTMost precious
RARESTMost coveted by collectors, perhaps
RARESTMost valuable, perhaps
RARESTSuperlatively red
RARESTLeast plentiful
RARESTMost seldom seen
RARESTLeast likely to be spotted
RARESTMost unique
RARESTLeast known
RARESTSuperlatively collectible
RARESTHardest to obtain.
RARESTMost admirable.
RARESTOf unusual excellence.
RARESTThinnest.
RARESTMost excellent.
RARESTMost uncommon.
RARESTLeast dense.
RARESTLeast seen.
RARESTHardest to find.
RARESTLeast common.
RARESTDescribing a numismatist's treasure
RARESTThinnest, as air.
RARESTMost singular
RARESTMost distinctive
RARESTMost exceptional
RARESTThinnest
RARESTChoicest
RARESTLeast dense
RARESTLike the best June day
RARESTLeast abundant