Rabbit ears.

Rabbits have independently focusable ears. When Vanilla is relaxing, she puts her ears down against her back. If I walk up to her, she will raise one ear and point it at me, as if to say, "don't try anything funny; I got my ear on you."

I think that's pretty cool. If you watch her ears, you can see what she's paying attention to with them. Of course, this is true of cats and other critters too, but rabbits have such huge ears that I find it so much more comical, like Bozo the Clown's oversize shoes.