I had a siamese kitty that was just like a dog. He would play fetch (literally, I'd throw the toy mouse, he'd go pick it up, drop it in my lap or on the floor. If I was sitting he'd wait till I threw it, but if I was standing he'd walk in circles and meow till I threw it for him! He also nicked a stuffed shark I had. The thing was half his size, and he would pick it up by the dorsal fin, toss it in the air, then attempt to catch it.
And he was forever loosing his toy mice. He'd wack it under the stove or fridge or chest freezer, then coming running to me, nagging me to get it out for him lol.
He was also really easy to train =)
Another cat I had, Abagail, was also really smart. She'd respond to conversation as if she understood. One time I had to cage her because I had a new kitten I was trying to get used to the outdoors (her only flaw was she hated other animals). She was crying and I told her to be quiet, it would only be for an hour. When she kept crying I told her that if she made one more sound, I would make it an hour and a half.
She then sat down, stopped crying, and I didn't hear a peep out of her until it was time for Alijah (the kitten) to go inside again!
Another time I was looking behind the garage for something, and Abbie followed me up there (the garage was right at the back of our yard). As I was leaving I walked over a piece of sheet metal. When I turned to see if Abbie was still following me, I found she'd sat down next to the sheet metal and was staring at it. I called her but she just looked at me then back at the metal.
So I went over to pick it up. Underneath was a small skink that had been half squashed but was still alive. I've no idea how she knew it was there, it was stuck in place because it was squashed

and they don't make noise! I put the poor little mite out of his misery, and only then did Abbie decide to follow me again.
My current kitty, Perrie, loves to chase rubber bands, and throw them in the air. But when he can't find them, he takes care of the fairy infestation in our house. He's often running around at all hours chasing those fairies lol.