This one is less of a surprise, but for me it's even more painful, because I grew up as a sci-fi nerd and Clarke was one of my trinity of favorite writers, along with Asimov and Bradbury.
Clarke's particular focus had to do with an expansive view of the universe, in which people are only a tiny part of a vast, grand cosmos, but with our own unique potential. His was an optimistic, humanistic voice that has been a huge influence on not just science-fiction but in popularizing science and making people aware of the larger world around that we all share.
But as he said last year on his 90th birthday, he mostly wanted to be known as a writer and as an entertainer, and he succeeded at that admirable: 2001, Rendezvous with Rama, Childhood's End, all terrifically entertaining and inspiring.
Also, he wasn't above wondering about ape-men and the Loch Ness monster: