I didn't mention this in the pros, but for those who already have chickens, rabbits integrate really nicely. You can set them up so that their droppings fall onto a carbon source and the chickens dig through and mix it all up for you. 

Droppings can also fall into worm bins, soldier fly bins, or duckweed, all of which are great for the birds.

Cute factor aside, they're way easier to butcher than chickens.