Cat ears generally, but it does depend on the character sometimes.
I love tails more than ears, though. Cat tails all the way, but fluffy fox tails can be nice, too, especially when they have several (usually, when more than one, it's 9 for foxes). Rabbit tails I never liked, too short.
Rabbit ears, too, are not very popular with me. It takes a lot for me to like Usagimimi.