Angel - I ended up spoiled for a lot just because I started watching late, but that I had no idea about at the time, and it was a treat. Especially since the Darla/Angelus of the flash backs really caught my attention.

Doctor Who - I totally knew and I was still on the edge of my seat, I think because Jacobi is Just That Awesome. I wish we could have kept him longer. (I love Simm, generally, but I have...issues with his Master. Which might have got foisted onto Jacobi's anyway, so.)