What poetic devices are used in "Richard Cory?"

The poetic devices used in "Richard Cory" by Edwin Arlington Robinson include sound devices, repetition devices, rhyme, and rhythm.

The sound devices that stand out are alliteration and consonance. Alliteration is the repetition of initial consonant sounds. The predominant initial consonant throughout the poem is /w/. Phrases with words in close proximity that start with /w/ are "whenever Richard Cory went down town" and "still we worked and waited for the light." The repetition of the /w/ sound can evoke the feeling of questioning (what? or why?) or a wail of sorrow or complaint. Another use of alliteration is "we people on the pavement," which repeats the /p/ sound. Consonance, repetition of internal or end consonant sounds, occurs in the words "fluttered" and "glittered." These are light sounding words, adding a sense of grace and ease to the description of Richard Cory.

Anaphora is the technique of repeating the same words at the beginning of successive clauses. We see this used in lines 5 and 6: "And he was always." Other lines also start with "and he" or simply "and." This technique binds the poem together and also gives the feeling that it is being narrated by someone close to the situation speaking in his own words. It also creates a monotony that makes the abrupt ending more surprising.

The poem has a formal rhyme scheme and rhythm. It is written in consistent iambic pentameter, meaning each line consists of ten syllables of alternating unaccented and accented stresses. The effect of this is to make the poem very steady and predictable, making the surprise ending come as more of a shock because the reader has been lulled by the very consistent and regular rhythm. Nothing in the words or their sounds has suggested  that something sudden or violent is going to occur, so the steadiness of the rhythm and meter, along with the regular abab rhyme scheme, forms a  stark, ironic contrast to the surprising ending.