Chickens. Over the years I've met numerous people who keep them and extol their virtues. I did some repairs on a chicken pen recently for my local community garden and now I get why people like the critters.
 The garden has adopted 6 hens which live in a very much larger coop most of the time and the smaller version is for use as a 'chicken tractor'. The idea is that chickens eat the grass, peck and scratch around and turn the soil over, manuring it as they go. We wondered if they'd have the instinct because these are rescue hens i.e. battery hens that have spent their existence till now in factory farming. The moment this hen was put in the grass it was off- pecking and scratching and pooing!
 I have known pigs to be used in a similar fashion with fencing that's moved around over an area to be "tractored" and it seems like chickens will do the same thing (albeit gentler) with eggs to boot. There must be more foxes around cities now than in the countryside so these hens will probably have to be in some kind of enclosure most of the time but they're certainly in a better place than they were.
 I read an article recently about someone who keeps chickens in a woodland with no need for pens and coops. Chickens are a woodland animal by nature and left to their own devices can flap up to the lower branches of trees to roost away from predators. One of those instances where nature has a plan and we've deviated from it.
 I must admit I was surprised how soothing it is to watch chickens go about their business; I've come to understand why so many people keep them as productive pets!