Fish like 'em too! Or at least the freshwater do (never got my saltwater tank set up). They go absolutely crazy chasing after it... I accidentally didn't move it in time, and my poor Gourami bonked his snout against the glass
I really wish I could use a laser pointer in the sport of catching fish in the pond. But it's illegal to use artificial light for attractants (you can have a light on/in your bobber, though, so you can see nibbles/bites)
My cats know the sound of the click when I turn the laser pointer on or off. I have to hold it tightly in my hand to muffle the sound or disguise it with a cough if I'm trying to surprise them with it.
Sometimes when I click a pen one of them will look around at me all excited. So then of course we have to play because I can't stand the disappointed looks on their little faces otherwise.