I try to change up the selection of poems for this assignment, and this quarter I assigned "The Cabbage" by Ruth Stone for the first time. The full text of the poem is available here on poets.org. I think the students enjoyed this poem. Rereading it again I find it's a good example of a poem that makes interesting use of "you" rather than "I" for its voice; I think this can be hard to pull off. This poem would be a good basis for a writing exercise in which you write a piece in the second-person voice.
Ruth Stone also has a great poem about having a burger at McDonald's, but it doesn't seem to be available online, alas.