...that don't actually (currently) exist. They could be things that are definitely impossible or things that may be possible in the future.
Some of my wishes:
Friendly, cuddly, mini-size lion/tiger species that I could have as pets, that could kill all the pests in and around the house, eat all the unwanted weeds, whose hair never comes off and that could act like security dogs.
A (mini-size) robot that is with me 24/7 and could make all the right decisions for me whenever I'm indecisive - such decisions as what career should I pursue?, which house should I buy?, which watermelon is the most delicious (in a supermarket)?, should I have coffee or tea in a given situation? etc.
Grapefruits that are smaller, thin-skinned, easy to peel and completely seedless - like mandarins.