I've seen them have remarkable relationships with horses—tough guy George (on his back, looking adorable in the second photo above—don't scratch that belly! It's a trap!) was best buds with a thoroughbred named Degas. When Degas was sick with Cushing's Disease, George hung out with Degas while he was isolated in a dry lot. He slept in Degas' feed box. And curled up back to back with Degas when he slept in his stall.
I love cats in general, but a barn cat is a special breed. Not feral, by any means, but not domestic, either. They are excellent mousers, scrappy survivors, and usually terrorize the farm's dogs.
A barn cat is nearly always very interesting character. Earning any cat's love is always a tougher feat that earning a dog's love, but when you're "in" and beloved of a barn cat, that's a real accomplishment!