Our new Mistress will hopefully be coming to live with us very soon.
The time we had a rescue cat come to live with us was 1998. I bought a carrier, a bed, a basic litter tray, a couple of bowls, a simple scratching post, a brush and a few toys. There wasn't a big range to choose from, so it was all fairly simple.
These days there seems to be a vast range of cat-related paraphernalia to choose from. I'm also lucky in that as well as being able to offer time and attention, I have more money to spend than I did twenty years ago. I've seen a number of cat-related products that weren't even invented last time I was preparing for a new feline family member.
While I'm waiting for the Mistress to arrive, I'd love to know what is the most useful thing you've bought for your cat, i.e. the thing you can't live without or wish you'd bought years ago.
(If there's anything that you feel was a complete waste of money, I'd be happy to hear about that too).