This is a tough one, because there are so many shows I have loved and lost due to fickle cancellation, but I am going to go with my dear, departed Terminator: The Sarah Connor Chronicles. If you never watched it, you're missing out on one of the most philosophical, meditative, yet action-packed and amazing SF shows to air in the last decade. It picks up from the Terminator mythos following Judgment Day, but then goes on its own unique way, really exploring the nature of what it means to be human, what it means to evolve, and what it means to be loyal. Wonderful acting from a fantastic cast, beautifully shot, and featuring the music of Battlestar Galactica composer Bear McCreary.
Day 1 - A happy gif