The definite article
some, a few, a particular one, a special one, a specific one, a certain one, an individual one, this, that, each, every, these, those, the whole, the entire.
Special or unique; often italics
preeminent, outstanding, particular, unparalleled, unequaled, supreme, unsurpassed, unusual, uncommon, rare, singular, unprecedented, exceptional, one, sole, single, significant, distinguished, especial, specific, choice, individual, peculiar, exceptional, occasional, unfamiliar, strange, spectacular, phenomenal, unheard of, unknown, unattainable, invincible, impregnable, almighty, all-powerful; see also special 1, unique 1.
Antonyms common*, usual, ordinary.