My one is just a relentless terminator. They have rid the house of spiders, flies and any other living insects.
The only downside is that if the insect is in some unreachable place, she will start causing havoc and chaos around the room, all in order to get at it.
Both of my cats are obsessed with flies. One of them is too shy/gentle, so she'll just chirp at it, but the other one will hear that chirping and immediately start hunting and subsequently eating that fly.