Watching a cricket or earthworm disappear into the green vortex of death is always fun. It's a slower process than watching darts eat (as far as I can tell from the videos).

I just got my dubia roaches, so I don't have many, but strangely I like them too. I wondered how the cockroach people wanted cockroaches as pets, but they're interesting to watch. Plus you don't have to chase them all over the living room when they hop out of your hand like crickets do.