Today would have been Robert A. Heinlein's 100th birthday, had he been as immortal as some of his characters.
It's no secret that, unlike some Heinlein fans I could name, I don't believe the man could do no wrong. He was too complex for that, and I strongly disagree with some of the things he said and wrote. I detest Farnham's Freehold and The Day After Tomorrow, was bored by I Will Fear No Evil and Time Enough For Love, and haven't even attempted to read The Number of the Beast or To Sail Beyond the Sunset (though I have recently been ploughing through his early attempt at a novel For Us, The Living, an intriguing if plotless diatribe written after his unsuccessful attempt to enter politics as a polyamorous nudist supporter of Upton Sinclair's EPIC. No, I'm not joking).
That said, if he'd written nothing but 'All You Zombies', 'The Unpleasant Profession of Jonathan Hoag', and 'The Man Who Traveled in Elephants', he would still (IMHO) be deserving of his Grand Master status. And as well as these gems, he also gave us 'The Long Watch', 'The Green Hills of Earth', 'The Man Who Sold the Moon', 'Requiem', Have Space Suit, Will Travel, Between Planets, Glory Road, and many other works that I've enjoyed reading and re-reading. While I'm no fan of Starship Troopers, I acknowledge its importance to the genre, if only for the "responses" and outright piss-takes it has inspired and which I have enjoyed.
His influence on the sf writing community has been immeasurable: to cite just one example, I am pleased and grateful his philosophy that the sf writers who he helped out in times of crisis (and there were many of them, some of whom disagreed fervently with his politics at the time), should not pay back these favours but "pay them forward", has been adopted by many others in the field.
Take him for all in all, the world would be a much poorer place had he never lived, and I can think of no higher praise for anyone.