Emissary (DS9) - I had bad memories of this one from first run, but I've watched it a couple of times recently and I think it's now my favourite pilot. It reflects the tone of the show that follows better than any of them, the characters seem far more real and developed, the actors seem already comfortable in their roles, and Avery Brooks is just wonderful. It's a story about the thrill of discovering the unknown, combined with a personal story about being stuck in the past and letting tragedy define your future. A joy to rewatch.