Theodore Sturgeon
Although Sturgeon is well-known among readers of classic science-fiction anthologies (at the height of his popularity in the 1950s he was the most anthologized author alive) and much respected by critics (John Clute writes in The Encyclopedia of Science Fiction: "His influence upon writers like Harlan Ellison and Samuel R. Delany was seminal, and in his life and work he was a powerful and generally liberating influence in post-WWII US sf"), he is not much known among the general public and won comparatively few awards (though it must be noted that his best work was published before the establishment and consolidation of the leading genre awards, while his later production was scarcer and weaker). He was listed as a primary influence of the much more famous Ray Bradbury.  Kurt Vonnegut based his character Kilgore Trout on Theodore Sturgeon.