Of recent celebrity deaths, William Goldman's is the one I mourn the most. I liked many of the movies he wrote, I was a fan of his novel The Princess Bride from long before it was a movie, and I absorbed his two big non-fiction books on movie-making, Adventures in the Screen Trade and Which Lie Did I Tell? I used his first law of moviemaking, "Nobody knows anything," as an anchor in my article on Peter Jackson's Lord of the Rings movies. Nobody knows anything; nobody knows what will succeed or fail; rules on what you have to do to the plot because it's a mooooovie are really no more than "what worked on the last successful blockbuster" and are liable to be overturned at any moment. I appreciated Goldman's work and his insights even in the anxious and highly-wrought context he expressed them in. He was a major figure in a precarious business.
Douglas Rain was an actor whose name few recognize, but they know him without realizing it. He was the voice of the HAL 9000 computer in 2001: A Space Odyssey. His creepy calmness was unforgettable, for reasons I've discussed. Some years ago, I saw a DVD of the 1957 Canadian Oedipus Rex film on an academic friend's desk; she was planning on showing it to her class. I pointed out the two unusual facts about that film: that it was the version that inspired Tom Lehrer to write his song of the same title as a "theme song" for the movie, and that the actor who played Creon went on to play HAL in 2001.
Fred Patten was an LA sf fan I would see around at conventions, but whom I didn't know personally. His command of his specialized areas of expertise, anime and furry fandom, was awesome, but they weren't part of my world.
Of Stan Lee I can merely say that I was aware of his existence. As with Gary Gygax, a figure whose death brought out the most startlingly deep mourning among many of my acquaintances, his work didn't mean much to me one way or another. But I'm not interested in denouncing it either. He did what he wanted to do, he pleased many, he acquired fame and, apparently, a degree of happiness. In Lee's own phrase, nuff said.