When I was fifteen or sixteen, I was browsing in a second-hand bookstore and happened to pick up a 1941 copy of "Twentieth-Century American Poetry" edited by Conrad Aiken, liked the look of it (it had TS Eliot's "Lovesong of J Alfred Prufrock" in it) and bought it. It is one of the few books that has traveled with me literally everwhere I have gone -- California, England, Boston, Philadelphia, Toronto, Oregon, St. Nowhere, St. Louis, Texas, and Chicago -- and it's near to coming apart at the seams between the dogears, the underlining, and the re-readings.
I didn't read it cover-to-cover until I was eighteen, but one of the poems that I did take an instant liking to at sixteen was EA Robinson's "Eros Turannos". I wouldn't encounter his most famous poem, "Richard Corey", until years later, when I was old enough to appreciate it, but I think my favourite is still Flammonde.
Flammonde
The man Flammonde, from God knows where,
With firm address and foreign air,
With news of nations in his talk
And something royal in his walk,
With glint of iron in his eyes,
But never doubt, nor yet surprise,
Appeared, and stayed, and held his head
As one by kings accredited.
( Erect, with his alert repose )