My grandpa's cat, Molly, a dilute Tortoiseshell, was the queen of grudges.
She loved me, and I had wanted to take her home when she was a kitten, but my mom wouldn't let me have her because she was so mean (to everyone but me). I was still in high school when Molly was born; she lived almost 20 years!
Grandpa had a large white dog and another cat; a black one with white paws named Mittens. Molly hated the dog and ESPECIALLY hated Mittens. My grandparents were allowed to be nice to the other cat and the dog, but I was not.
One time, Grandpa and I went out to eat together and bright back meat for the animals. I gave some to Molly, and while she had her back to me eating, I slipped a big piece of steak to the dog. Just then, Molly turned around and saw it, and she was PISSED. For the next few days, she refused to have anything to do with me.
Another time, Mittens ran past Molly and jumped in my lap and curled up to sleep. Molly sat in front of me on the ground with her back to me and refused to even look at me. I got up and moved to the other side of the room, and the cat turned around again to keep her back to me. She did that every time I visited for the next SIX WEEKS before she forgave me for letting that other cat on my lap!