Rabbit
What it does: It hops around being adorable and elusive.
How to make it:
Rabbits typically do well enough at making more Rabbits, but if you want to do it yourself, you can get a Daemon Bunnae to eat a Fire. This will also get you a Copper.
You can also throw a Forest Shrine at a Doom Spirit.
Or you can let a Wolf eat another animal. A Rabbit will be the byproduct.
What it makes:
It makes some child-crazed young townsfolk like you more, but you can also create some things. Like a Daemon Bunnae, if you really want one.
And a Rabbit and an Ancient Mortar will get you a Berry.