My 5 year old son loves anything to do with nature. But he particularly likes predators. And snakes are a big favorite, especially the venomous ones. He says he wants to be an explorer when he grows up (I have a feeling he would miss his home comforts a bit too much for that!) but he's enjoying making plans.
He knows someone who keeps real snakes. But I don't fancy that! So he'll have to make do with the toy variety. There are some excellent snake toys around though.