Just finished watching the final of Blake's 7. Wow - I totally wasn't expecting that. I'd heard it was a good ending, but no one spoiled it for me, which is pretty amazing since this first aired in 1981.
If you want to know what I'm talking about, go here. This wiki article later claims this final episode as an "unresolved cliffhanger". I can't think of anything unresolved here. It is OVER.
I really enjoyed it anyway.
I think one of my favourite episodes was S4E10 - "Gold". This is the only episode in which Servelan gets one over the crew, and it's a double whammy as well, with the reveal only happening in the last minute. While the rest of the crew are devastated, Avon gets this massive grin on his face, and laughs maniacally until the credits roll. It's just beautiful. He really is quite unhinged by the end of series 4, and by far my favourite character.