WordNet (r) 3.0 (2006):

number one
    n 1: a reference to yourself or myself etc.; `take care of
         number one' means to put your own interests first
    2: the first or highest in an ordering or series; "He wanted to
       be the first" [syn: first, number one]
    3: the first element in a countable series; "the first of the
       month" [syn: first, number one, number 1]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "number one":
   Al, Grade A, alter, alter ego, alterum, better self, blue-ribbon,
   capital, cock, dominant, ego, ethical self, first-class,
   first-rate, first-string, he, her, herself, him, himself,
   inner man, inner self, it, main, major, me, my humble self, myself,
   oneself, other self, ourselves, outstanding, predominant,
   preeminent, self, she, stellar, subconscious self, subliminal self,
   superego, superior, them, themselves, they, you, yours truly,
   yourself, yourselves