Shadow of the Cat
I'm surprised this isn't your favorite Hammer film, Hammerfan!
Absolutely loved this. Beautiful love story between an old lady and her beloved pet and best friend. The deaths were so clever you'd almost swear some of them the cat was just being an innocent cat and the people just ended up dead by their own dumbass faults. The characters were terrible people that I was just delighted to watch die.
Damn I wish I had recorded it...