Anything by/with Sir David Attenborough.
I recently watched a Documentary called 'The Secret Life of Dogs' narrated by Martin Clunes, and it was absolutely amazing. Some really incredible stories and some fascinating science behind man's best friend
If you're a dog person and haven't seen it, do. It's awesome.
Really enjoyed Brian Cox's 'Wonders of the Solar System' and 'Wonders of the Universe' as well.