What other pets should be avoided if you have a cat?

I had a mini zoo when I was a kid - guinea pigs, hamsters, gerbils, turtles, fish... and a cat. The cat knew to leave the other critters alone, though he and the guinea pig became best friends. We'd often catch him hanging out near the cage, and if we took the piggie out around the cat, they'd snuggle up together. When the piggie died, the cat sat where the cage had been and howled because he missed his buddy.