Rose's memory (motif)
Rose's uncannily sensitive and accurate memory is her whole reason for becoming involved in the actions of the story: Pinkie, visiting her at Snow's, finds that she remembers Spicer's face very clearly. Later on, throughout his relationship with her, Pinkie is frustrated by the way in which she seems to remember all the things he doesn't want her to and neglect all the things he wants her to.
Colleoni's clockwork view of the world (symbol)
When Pinkie goes to meet him at the Cosmopolitan, Mr. Colleoni outlines a view of the world in which the rough and violent world of gangsters such as Pinkie has its energies redirected into a much cleaner, more prosperous, and more bureaucratic form of organization. One of the symbols he uses to express this vision is that of the many clocks of world times at Greenwich.
Vitriol (symbol)
The bottle of vitriol that Pinkie carries around is perhaps the strongest symbol for his, frankly, vitriolic character: he causes indiscriminate pain and hides this capability within a compact frame. Eventually, the weapon is fated to turn on the hand that uses it, but it is also important to note how Rose does not take note of it; this, in turn, represents her accommodating attitude towards Pinkie himself.
The broken-down Morris (symbol)
The cheap and broken-down car that Pinkie drives, often stalking people such as Hale in the beginning when he is about to murder him, represents Pinkie's aspiration (given the importance of a car as a status symbol) and, simultaneously, his lowly position.
Ida's investigation (allegory)
Ida harangues Rose and tries to separate her from Pinkie, not so much out of a sense of justice, but rather from a supposedly philanthropic impulse. This makes her whole kindhearted enterprise, prying into the affairs of other people where she is not involved and secularizing religious beliefs, stand as an allegory for the different ways in which progressives try to effect social change.
