As far as my own native field of sf/fantasy goes, she was one of the giants in the earth. The Left Hand of Darkness was groundbreaking, and it’s the book that’s getting namechecked in the obits, though I personally liked The Dispossessed better. (She depicted the only fictional utopia I could actually imagine existing – not one that I would want to live in even if you paid me, but one that I could believe might be real.) As for her fantasy – I read A Wizard of Earthsea during the summer between my senior year in high school and my freshman year in college, and it made the top of my head come off.
Good-bye, Ursula, and thanks. It was an honor to share a genre with you.